Osisko Windfall Infill Drilling Continues to Intersect High Grade

88.0 g/t Au Over 4.1 Metres in Underdog

131 g/t Au Over 2.1 Metres in Lynx

59.9 g/t Au Over 2.6 Metres in Zone 27

9.56 g/t Au Over 12.6 Metres in Caribou

TORONTO, March 19, 2019 - Osisko Mining Inc. (OSK:TSX. "Osisko" or the "Corporation") is pleased to provide new infill drilling results from the ongoing definition and expansion program at its 100% owned Windfall gold project located in the Abitibi greenstone belt, Urban Township, Eeyou Istchee James Bay, Québec. The program is currently focussed on infill drilling within the main Windfall gold deposit and the adjacent Lynx deposit (located immediately NE of Windfall), exploration and expansion drilling on the main mineralized zones, and deep exploration in the central areas of the intrusive system. Significant new analytical results from 101 intercepts in 39 drill holes and 17 wedges focused on infill drilling from surface and underground are presented below.

Highlights from new infill drilling results include: 88.0 g/t Au over 4.1 metres in OSK-EAG-13-480-W2; 131 g/t Au over 2.1 metres in OSK-W-18-1656; 128 g/t Au over 2.0 metres in OSK-W-19-909-W8; 85.1 over 3.0 metres in OSK-W-18-1066-W3; 54.4 g/t Au over 3.1 metres in OSK-W-18-1386-W5; 59.9 g/t Au over 2.6 metres in WST-19-0060; 45.0 g/t Au over 3.0 metres in OSK-W-19-1426-W1; 9.56 g/t Au over 12.6 metres in OSK-W-19-1823; 52.9 g/t Au over 2.1 metres in OSK-W-18-1813; 34.9 g/t Au over 2.4 metres in OSK-W-19-1819-W1; 38.2 g/t Au over 2.0 metres in OSK-W-18-1759; 34.5 g/t Au over 2.2 metres in OSK-EAG-13-480-W1; 13.2 g/t Au over 4.9 metres in OSK-W-19-1343-W3; 9.37 g/t Au over 6.0 metres in OSK-W-18-1803; and 8.98 g/t Au over 6.4 metres in WST-18-0039. Maps showing hole locations and full analytical results are available at www.osiskomining.com.

Notes: Ex = Expansion. VNCR = Crustiform Vein. True widths are estimated at 65 – 80% of the reported core length interval.
See "Quality Control and Reporting Protocols" below.

Note: WST series drill holes were completed from underground drill stations.

OSK-EAG-13-480-W1 intersected 5.98 g/t Au over 6.4 metres and 34.5 g/t Au over 2.2 metres in Underdog. The first interval is composed of up to 10% disseminated pyrite stringers and clusters with quartz veinlets or pervasive silica flooding, trace chalcopyrite and sphalerite and local visible gold. Mineralization is hosted in a sericite altered porphyritic felsic dike. The second interval contains local visible gold, 7% pyrite in pervasive silica flooding, and up to 5% pyrite stringers within a sericite altered porphyritic felsic dike.

OSK-EAG-13-480-W2 intersected 3.93 g/t Au over 2.7 metres and 88.0 g/t Au over 4.1 metres in Underdog. The first interval is composed of up to 7% disseminated pyrite and stringers with local pervasive silica flooding, trace disseminated chalcopyrite and sphalerite and pyrite-tourmaline stringers within a strong biotite and sericite altered fragmental felsic dike. The second interval contains local visible gold and electrum in quartz cluster veins, up to 20% disseminated and stringer pyrite, ptygmatic tourmaline veins and traces of chalcopyrite. The mineralization is hosted in a moderately to strongly sericitized porphyritic felsic dike.

OSK-EAG-13-508 intersected 11.6 g/t Au over 2.4 metres in Zone 27. Mineralization is composed of 3% pyrite stringers and 1% pyrite clusters in a moderately bleached and sericitized andesite.

OSK-W-17-960 intersected two intervals in Lynx: 7.06 g/t Au over 2.2 metres and 13.7 g/t Au over 2.1 metres. The two intervals contain local visible gold, disseminated chalcopyrite and pyrite in a decimetre scale smoky-quartz vein, 3% pyrite-tourmaline stringers, and 1% chalcopyrite and sphalerite clusters in a silicified and sericitized rhyolite.

OSK-W-17-993 intersected 5.95 g/t Au over 2.3 metres in Lynx. Mineralization is composed of local visible gold, 2% pyrite, trace arsenopyrite, chalcopyrite and sphalerite within a smoky quartz vein (3 cm wide) at the contact with a sheared andesite and a massive rhyolite, all moderately silicified and sericitized.

OSK-W-18-747-W2 intersected three intervals in Underdog: 8.58 g/t Au over 2.5 metres, 7.10 g/t Au over 2.5 metres and 4.86 g/t Au over 2.0 metres. The first interval is composed of 5% pyrite-tourmaline stringers with pervasive silica flooding including a 15% pyrite interval 40 cm wide hosted in a moderate sericite and silica altered rhyolite. The second interval is composed of 5% pyrite, trace chalcopyrite in pervasive silica flooding and quartz-tourmaline veins (locally ptygmatic) hosted in a moderate sericite and silica altered felsic porphyritic intrusion in contact with a gabbro. The third interval is composed of 3% pyrite stringers, 3% pyrite stockwork and pervasive silica flooding in a sericitized, silicified and bleached porphyritic felsic dike.

OSK-W-18-1025-W1 intersected three intervals in Underdog: 13.9 g/t Au over 2.0 metres, 14.0 g/t Au over 2.0 metres and 4.67 g/t Au over 2.1 metres. The first interval is composed of 5% pyrite in pervasive silica flooding and 1% disseminated pyrite in a sericitized porphyritic dike with weak fuchsite alteration. The second and third intervals contain local visible gold, 5% pyrite in pervasive silica flooding and ptygmatic tourmaline veins, and up to 1% chalcopyrite in a moderately sericitized and silicified porphyritic felsic intrusion.

OSK-W-18-1066-W2 intersected three intervals in Underdog; 6.76 g/t Au over 2.0 metres, 23.3 g/t Au over 2.0 metres and 7.55 g/t Au over 2.0 metres. The first interval contains up to 5% pyrite with pervasive silica flooding and local ptygmatic tourmaline veins hosted in a moderately sericitized and silicified felsic porphyritic intrusion. The last two intervals contain trace pyrite stringers and pyrite-tourmaline stringers in a weakly sericitized porphyritic felsic dike.

OSK-W-18-1066-W3 intersected 5.24 g/t Au over 4.2 metres and 85.1 g/t Au over 3.0 metres in Underdog. The first interval contains 3% disseminated pyrite and stringers, up 15% pyrite with pervasive silica alteration, local visible gold, and sphalerite and chalcopyrite within a silicified porphyritic felsic dike. The second interval contains local visible gold in fracture filling and stringers, up to 20% pyrite, trace sphalerite and chalcopyrite with pervasive silica flooding hosted in a moderately sericitized and bleached felsic porphyritic intrusion.

OSK-W-18-1139-W1 intersected 5.65 g/t Au over 2.3 metres corresponding with a quartz vein with trace pyrite at the contact between two porphyritic felsic dikes with moderate sericite alteration and weak silica and fuchsite alteration.

OSK-W-18-1139-W3 intersect two intervals in Underdog: 6.46 g/t Au over 2.6 metres and 5.26 g/t Au over 2.2 metres. The first interval contains 10% pyrite associated with pervasive silica flooding in a sericitized and silicified felsic porphyritic intrusive. The second interval contains 20% pyrite as clusters inside a pervasive silica flooded interval 20 cm wide hosted in a sericitized and silicified felsic porphyritic intrusive at the contact with a small felsic porphyritic fragmental dike.

OSK-W-18-1386-W4 intersected five intervals in Lynx: 12.1 g/t Au over 2.4 metres, 11.7 g/t Au over 4.0 metres, 10.7 g/t Au over 2.5 metres, 9.43 g/t Au over 2.0 metres and 8.22 g/t Au over 2.0 metres. The first interval contains up to 7% disseminated pyrite, 3% pyrite and trace chalcopyrite in quartz-tourmaline veins, 3% pyrite clusters and trace pyrite stringers in a sericitized and weak silica and fuchsite altered gabbro. The last four intervals contain local visible gold, up to 5% pyrite as clusters and stringers, 1% sphalerite, and trace chalcopyrite in pervasive silica flooding hosted in a silicified, sericitized and fuchsite altered gabbro or sericitized and silicified rhyolite.

OSK-W-18-1386-W5 intersected 54.4 g/t Au over 3.1 metres in Lynx. Mineralization is composed of local visible gold, 4% disseminated, clustered and stringer pyrite, and trace chalcopyrite with quartz-tourmaline veins and pervasive silica flooding hosted in a strongly bleached, silicified and fuchsite altered gabbro.

OSK-W-18-1424-W1 intersected 5.60 g/t Au over 2.0 metres in Lynx. Mineralization is composed of tourmaline-quartz veins with trace pyrite hosted in a sericitized gabbro.

OSK-W-18-1656 intersected 5.07 g/t Au over 6.0 metres, 8.08 g/t Au over 2.3 metres, 131 g/t Au over 2.1 metres and 7.29 g/t Au over 2.5 metres in Lynx. The first and second intervals contain 1% disseminated and stringer pyrite in a moderately sericitized and weakly silicified porphyritic felsic dike. The third interval contains up to 3% pyrite stringers with silica flooding hosted in a strong silica altered rhyolite. The last interval contains 5% pyrite stringers and trace chalcopyrite within a moderate sericite altered gabbro.

OSK-W-18-1680 intersected 9.92 g/t Au over 2.5 metres in Zone 27. Mineralization is composed of up to 5% disseminated pyrite, 1% pyrite stringers and quartz carbonate veins hosted in a moderately sericitized felsic porphyritic intrusion with small quartz eyes.

OSK-W-18-1738 intersected 8.22 g/t Au over 2.0 metres in Lynx. Mineralization is composed of traces of disseminated and clustered pyrite in a moderately chlorite, silica and carbonate altered gabbro.

OSK-W-18-1747 intersected two intervals in Caribou: 5.99 g/t Au over 2.4 metres and 3.09 g/t Au over 2.7 metres. The first interval contains up to 7% pyrite stringers in pervasive silica flooding in a moderately sericitized and silicified felsic porphyritic intrusion. The second interval contains 4% disseminated and stringer pyrite in a sericite and fuchsite altered gabbro.

OSK-W-18-1759 intersected 38.2 g/t Au over 2.0 metres in Lynx. Mineralization is composed of local visible gold and up to 20% pyrite in pervasive silica flooded zones in a moderately sericitized and patchy silicified felsic intrusion.

OSK-W-18-1779 intersected 4.05 g/t Au over 2.1 metres in Caribou. Mineralization is composed of up to 40% semi-massive pyrite, 10% disseminated pyrite, 7% pyrite stringers and 1% pyrite clusters in a bleached sericitized and silicified andesite.

OSK-W-18-1789 intersected 3.87 g/t Au over 2.0 metres in Caribou. Mineralization is composed of 1% pyrite stringers and trace chalcopyrite in pervasive silica flooding in a sericitized porphyritic felsic intrusion.

OSK-W-18-1803 intersected 3.74 g/t Au over 2.0 metres in Caribou and 9.37 g/t Au over 6.0 metres in Zone 27. The first interval contains 1% pyrite clusters and traces of chalcopyrite in a bleached and foliated andesite. The second interval contains local visible gold, up to 6% pyrite clusters and trace chalcopyrite hosted in moderate to strong sericitized fragmental andesite in contact with a felsic porphyritic intrusion.

OSK-W-18-1805 intersected three intervals in Caribou: 3.76 g/t Au over 4.2 metres, 3.48 g/t Au over 4.2 metres and 9.59 g/t Au over 2.0 metres. Mineralization is composed of semi-massive pyrite bands locally up to 70% pyrite, 5% disseminated pyrite and 4% pyrite stringers hosted in a slightly foliated, sericitized and silicified felsic porphyritic intrusion.

OSK-W-18-1806 intersected 3.74 g/t Au over 2.0 metres in Caribou. Mineralization is composed of 1% disseminated pyrite and trace pyrite stringers in a moderate sericite, chlorite and weak silica altered porphyritic felsic dike.

OSK-W-18-1808 intersected two intervals in Caribou: 23.8 g/t Au over 2.3 metres and 13.8 g/t Au over 2.0 metres. The first interval contains up to 5% pyrite within quartz-tourmaline veins and trace pyrite with tourmaline-ptygmatic veinlets at the contact between a sericitized and weakly foliated rhyolite and a felsic porphyritic intrusion. The second interval contains up to 5% pyrite-tourmaline stringers and 2% disseminated pyrite at the contact between a sericitized and patchy silicified porphyritic felsic dike and a rhyolite.

OSK-W-18-1810 intersected two intervals: 3.35 g/t Au over 2.0 metres in Caribou and 5.86 g/t Au over 2.0 metres in Zone 27. The first interval contains clustered quartz and tourmaline-quartz veins in a chlorite, hematite and carbonate altered andesite. The second interval contains up to 5% pyrite stringers with local stockwork texture hosted in weakly to moderately brecciated and bleached andesite in contact with a felsic porphyritic intrusion.

OSK-W-18-1813 intersected four intervals in Caribou: 52.9 g/t Au over 2.1 metres, 15.8 g/t Au over 2.1 metres; 5.54 g/t Au over 2.1 metres and 4.38 g/t Au over 2.2 metres. The first interval contains trace pyrite-tourmaline stringers and 1% pyrite in quartz-tourmaline veins in a chloritized, weakly sericitized and silicified gabbro. The second interval contains 8% disseminated pyrite, in cluster or fracture filling, and trace pyrite and chalcopyrite with quartz-tourmaline veins in a bleached and sericitized andesite. The third interval contains 3% pyrite stringers in a weakly bleached andesite. The fourth interval contains up to 15% pyrite stringers and 5% disseminated pyrite with pervasive silica flooding hosted in a moderately bleached andesite in contact with a moderately sericitized porphyritic felsic dike.

OSK-W-18-1814 intersected four intervals in Caribou: 4.04 g/t Au over 2.0 metres, 13.2 g/t Au over 2.0 metres, 3.56 g/t Au over 2.0 metres and 8.19 g/t Au over 2.0 metres. The first interval contains 3% pyrite stringers, 1% disseminated pyrite and 5% quartz clusters in a chloritized andesite. The second interval contains trace disseminated pyrite, 2% pyrite stringers, trace quartz clusters in a sericitized and weak silica altered rhyolite. The third interval contains quartz-carbonate veins with trace pyrite at the contact between a rhyolite and a gabbro. The fourth interval contains traces of disseminated pyrite and pyrite-tourmaline stringers in pervasive silica flooding, within a sericite altered porphyritic felsic dike.

OSK-W-18-1817 intersected three intervals: 3.45 g/t Au over 2.0 metres and 7.60 g/t Au over 2.0 metres in Caribou and 5.93 g/t Au over 2.3 metres in Zone 27. The first interval contains trace pyrite-tourmaline stringers in a moderately sericitized, silicified and bleached porphyritic felsic dike. The second interval contains 8% pyrite as fragments inside a brecciated zone hosted in a strongly sericitized and moderately silicified felsic porphyritic intrusion. The third interval contains 5% pyrite stringers in a moderately bleached and sericitized, weak silica altered porphyritic felsic dike.

OSK-W-19-909-W6 intersected 6.00 g/t Au over 2.0 metres and 14.5 g/t Au over 2.6 metres in Lynx. The first interval contains 5% disseminated pyrite, 1% pyrite stringers with local centimetre-scale pyrite clusters in a moderately bleached and sericitized gabbro. The second interval contains local visible gold in quartz-carbonate shear-extension veins, up to 10% pyrite stringers, 3% ptygmatic tourmaline veins and trace chalcopyrite hosted in a moderate sericite altered gabbro.

OSK-W-19-909-W8 intersected 128 g/t Au over 2.0 metres and 8.39 g/t Au over 2.0 metres in Lynx. The first interval contains local visible gold hosted in pervasive silica flooding within a moderately sericitized rhyolite. The second interval contains 5% pyrite stringers and clusters in a moderately sericitized rhyolite.

OSK-W-19-909-W9 intersected 4.86 g/t Au over 2.0 metres in Lynx. Mineralization is composed of 2% pyrite stringers, traces ptygmatic tourmaline veins in a weakly sericitized porphyritic felsic dike.

OSK-W-19-1343-W3 intersected 13.2 g/t Au over 4.9 metres in Lynx. Mineralization is composed of 3% pyrite stringers, 5% disseminated pyrite with smoky quartz veins and quartz-tourmaline veinlets in a strongly silica altered rhyolite.

OSK-W-19-1426-W1 intersected 4.23 g/t Au over 2.1 metres, 6.48 g/t Au over 2.4 metres and 45.0 g/t Au over 3.0 metres in Lynx. The first interval contains 5% pyrite clusters and fragments, 1% pyrite stringers in a strongly silicified and moderately sericitized fragmental felsic dike. The second interval contains traces of disseminated pyrite within a strong carbonate, moderate sericite and chlorite altered andesite. The third interval contains 5% pyrite and trace chalcopyrite with pervasive silica flooding, and trace pyrite stringers at a silicified contact between a gabbro and a porphyritic felsic unit.

OSK-W-19-1819-W1 intersected 5.63 g/t Au over 2.0 metres and 34.9 g/t Au over 2.4 metres in Lynx. The first interval contains 3% pyrite stringers and 2% pyrite clusters within a strong silica and sericite altered andesite. The second interval contains 2% pyrite stringers and trace tourmaline-pyrite veins hosted in a moderate sericite altered rhyolite.

OSK-W-19-1820 intersected 4.26 g/t Au over 2.0 metres in Caribou. Mineralization is composed of 1% pyrite clusters with quartz veins within a weakly sericitized and silicified porphyritic felsic dike.

OSK-W-19-1822 intersected 4.39 g/t Au over 2.0 metres in Caribou. Mineralization is composed of 1% pyrite in clustered quartz veins within a chloritized and weakly sericitized and silicified bleached andesite.

OSK-W-19-1823 intersected 3.77 g/t Au over 2.0 metres and 9.56 g/t Au over 12.6 metres in Caribou. The first interval contains 3% pyrite-tourmaline stringers hosted in a silicified and weakly sericitized rhyolite. The second interval contains up to 25% pyrite stringers, clusters or disseminated, within strong pervasive silica flooding hosted in a silicified and moderately sericitized rhyolite.

OSK-W-19-1824 intersected 3.29 g/t Au over 7.0 metres in Caribou. Mineralization is composed of 2% pyrite-tourmaline stringers within a sericitized and silicified porphyritic felsic dike.

OSK-W-19-1828 intersected 5.09 g/t Au over 2.5 metres in Caribou. Mineralization is composed of up to 7% pyrite with crustiform quartz veins, 3% pyrite stringers, 1% pyrite associated with quartz-tourmaline veins, 2% disseminated pyrite and 1% pyrite clusters within a silicified and sericitized rhyolite.

OSK-W-19-1830 intersected 8.84 g/t Au over 2.6 metres in Caribou. Mineralization is composed of up to 5% disseminated and stringer pyrite, 10% pyrite clusters, and 1% pyrite associated with ptygmatic tourmaline veins and trace sphalerite and chalcopyrite in quartz-carbonate veins hosted in a sericitized porphyritic felsic dike.

OSK-W-19-1832 intersected 3.63 g/t Au over 2.2 metres and 4.06 g/t Au over 2.0 metres in Lynx. The first interval contains local visible gold, 1% sphalerite and 5% pyrite associated with a 20 cm-wide quartz-carbonates-tourmaline vein hosted in weakly sericitized rhyolite. The second interval contains 4% pyrite-tourmaline with silica patches and traces pyrite-tourmaline stringers in weakly sericitized rhyolite.

OSK-W-19-1834 intersected 12.4 g/t Au over 2.8 metres in Caribou. Mineralization is composed of up to 10% disseminated pyrite, 5% pyrite clusters, 2% pyrite stringers, 2% pyrite associated with quartz-carbonate veins, 2% interstitial sphalerite and trace disseminated chalcopyrite hosted in a sericitized and silicified fragmental felsic dike.

OSK-W-19-1847 intersected 7.18 g/t Au over 2.3 metres in Lynx. Mineralization is composed of up to 5% disseminated, stringer, and clustered pyrite with weak to moderate pervasive silica flooding and traces of disseminated pyrite with local quartz-tourmaline veins hosted in a strongly sericitized and moderately chloritized rhyolite.

WST-18-0027 intersected 11.1 g/t Au over 2.0 metres in Zone 27. Mineralization includes 1% disseminated pyrite within a moderate silica altered porphyritic felsic dike. WST-18-0027 was drilled from underground drill station AN-140-270-S located 140 metres below surface on section 2575E.

WST-18-0039 intersected two intervals: 3.82 g/t Au over 2.0 metres in Zone 27 and 8.98 g/t Au over 6.4 metres in Caribou. The first interval contains 5% disseminated pyrite with pervasive silica flooding within a moderate silica and sericite altered rhyolite. The second interval contains 5% disseminated pyrite with pervasive silica flooding and quartz-tourmaline veins within a moderate silica and sericite altered rhyolite. WST-18-0039 was drilled from underground drill station AN-160-020-S located 160 metres below surface on section 2250E.

WST-18-0048 intersected 4.67 g/t Au over 2.0 metres in Zone 27. Mineralization includes 2% pyrite stringers within a moderate sericite altered andesite. WST-18-0048 was drilled from underground drill station AN-160-020-S located 160 metres below surface on section 2250E.

WST-19-0054A intersected 9.37 g/t Au over 2.7 metres in Zone 27. Mineralization includes local visible gold, 15% semi-massive pyrite and 1% pyrite-tourmaline stringers hosted in a moderate sericite altered porphyritic felsic intrusion. WST-19-0054A was drilled from underground drill station BM-150-960-S located 150 metres below surface on section 2175E.

WST-19-0055 intersected 4.87 g/t Au over 2.0 metres. Mineralization includes up to 1% semi-massive pyrite, 5% pyrite stringers and 7% pyrite clusters hosted in a moderately sericite and weakly fuchsite altered gabbro and in a moderately sericitized dacite. WST-19-0055 was drilled from underground drill station BM-150-960-S located 150 metres below surface on section 2175E.

WST-19-0056 intersected 3.57 g/t Au over 4.8 metres in Zone 27. Mineralization includes up to 3% pyrite clusters with quartz-carbonate veinlets and up to 5% pyrite stringers in a moderately sericitized and locally hematized rhyolite in contact with a felsic porphyritic intrusion. WST-19-0056 was drilled from underground drill station BM-150-960-S located 150 metres below surface on section 2175E.

WST-19-0057 intersected 4.99 g/t Au over 4.7 metres and 4.47 g/t Au over 2.2 metres in Zone 27. The first interval contains up to 5% pyrite stringers with patchy silica, 2% disseminated pyrite, up to 15% pyrite as clusters and stringers hosted in a silica altered rhyolite in contact with a felsic porphyritic intrusion. The second interval contains 1% pyrite stringers with quartz veins at the contact between a porphyritic felsic dike unit and a gabbro. WST-19-0057 was drilled from underground drill station BM-150-960-S located 150 metres below surface on section 2175E.

WST-19-0058 intersected 3.08 g/t Au over 4.7 metres in Zone 27. Mineralization includes 2% pyrite-tourmaline stringers, trace pyrite clusters, and 1% chalcopyrite clusters hosted in a strong sericite and weak silica altered dacite. WST-19-0058 was drilled from underground drill station BM-150-960-S located 150 metres below surface on section 2175E.

WST-19-0059 intersected four intervals in Zone 27: 5.16 g/t Au over 2.7 metres, 4.04 g/t Au over 3.9 metres, 14.8 g/t Au over 2.2 metres, and 4.08 g/t Au over 2.3 metres. The first interval contains 3% tourmaline ptygmatic veins, 4% pyrite in a semi-massive band, 3% quartz-tourmaline veins in a moderately sericitized, silicified and local fuchsite altered porphyritic felsic dike. The second interval contains up to 10% pyrite with a ptygmatic tourmaline vein, 5% pyrite semi-massive with silica patches, 1% pyrite stringers and 1% disseminated pyrite within a sericite, silica and fuchsite altered porphyritic felsic dike. The third interval contains 2% pyrite stringers, and trace disseminated pyrite within a sericitized porphyritic felsic dike. The fourth interval contains 4% disseminated pyrite, 2% arsenopyrite clusters and trace chalcopyrite in a breccia zone hosted in a porphyritic fragmental felsic intrusion. WST-19-0059 was drilled from underground drill station BM-150-960-S located 150 metres below surface on section 2175E.

WST-19-0060 intersected 4.72 g/t Au over 3.1 metres, and 59.9 g/t Au over 2.6 metres in Zone 27. The first interval contains up to 40% pyrite stringers and trace pyrite clusters within a moderate sericite and weak silica altered rhyolite. The second interval contains traces pyrite and pyrite-tourmaline stringers within a moderate sericite and fuchsite altered dacite. WST-19-0060 was drilled from underground drill station BM-150-960-S located 150 metres below surface on section 2175E.

WST-19-0063 intersected 15.0 g/t Au over 2.0 metres in Zone 27. Mineralization includes 2% semi-massive pyrite, up to 7% pyrite with ptygmatic tourmaline veins, 1% pyrite stringers and trace disseminated pyrite hosted in a weakly sericitized and patchy fuchsite altered felsic porphyritic intrusion. WST-19-0063 was drilled from underground drill station BM-150-960-S located 150 metres below surface on section 2175E.

WST-19-0065A intersected 12.0 g/t Au over 3.5 metres. Mineralization includes up to 3% pyrite stringers, 5% pyrite with quartz tourmaline veins and 3% disseminated pyrite hosted in a weakly to moderately sericitized dacite. WST-19-0065A was drilled from underground drill station BM-150-960-S located 150 metres below surface on section 2175E.

Qualified Person
The scientific and technical content of this news release has been reviewed, prepared and approved by Mr. Louis Grenier, M.Sc.A., P.Geo. (OGQ 800), Project Manager of Osisko's Windfall Lake gold project, who is a "qualified person" as defined by National Instrument 43-101 – Standards of Disclosure for Mineral Projects ("NI 43-101").

Quality Control and Reporting Protocols
True width determination is estimated at 65-80% of the reported core length interval for the zone. Assays are uncut except where indicated. Intercepts occur within geological confines of major zones but have not been correlated to individual vein domains at this time. Reported intervals include minimum weighted averages of 3.0 g/t Au diluted over core lengths of at least 2.0 metres. All NQ core assays reported were obtained by either 1-kilogram screen fire assay or standard 50-gram fire-assaying-AA finish or gravimetric finish at (i) ALS Laboratories in Val d'Or, Québec, Thunder Bay, Ontario, Sudbury, Ontario or Vancouver, British Colombia, or (ii) Bureau Veritas in Timmins, Ontario. The 1-kilogram screen assay method is selected by the geologist when samples contain coarse gold or present a higher percentage of pyrite than surrounding intervals. Selected samples are also analyzed for multi-elements, including silver, using an Aqua Regia-ICP-AES method at ALS Laboratories. Drill program design, Quality Assurance/Quality Control ("QA/QC") and interpretation of results is performed by qualified persons employing a QA/QC program consistent with NI 43-101 and industry best practices. Standards and blanks are included with every 20 samples for QA/QC purposes by the Corporation as well as the lab. Approximately 5% of sample pulps are sent to secondary laboratories for check assay.

About the Windfall Lake Gold Deposit
The Windfall Lake gold deposit is located between Val-d'Or and Chibougamau in the Abitibi region of Québec, Canada. The mineral resource defined by Osisko, as disclosed in the Windfall Lake Technical Report (as defined below) and November 27, 2018 Lynx resource update, comprises 2,874,000 tonnes at 8.17 g/t Au (754,000 ounces) in the indicated mineral resource category and 10,352,000 tonnes at 7.11 g/t Au (2,366,000 ounces) in the inferred mineral resource category. For details regarding the key assumptions, parameters and methods used to estimate the mineral resources presented in respect of the Windfall Lake gold project, please see the technical report entitled "Technical Report and Mineral Resource Estimate for the Windfall Lake Project, Windfall Lake and Urban-Barry Properties" and dated June 12, 2018 (effective date of May 14, 2018), which has been prepared by InnovExplo Inc. from Val-d'Or, Québec (the "Windfall Lake Technical Report") and the press release “Osisko Releases Mineral Resource Update for Lynx” dated November 27, 2018, which has been prepared by Osisko and reviewed and approved by Micon International, Ltd. from Toronto, Ontario. The Windfall Lake Technical Report and press release are available on Osisko's website at www.osiskomining.com and on SEDAR under Osisko's issuer profile at www.sedar.com. The Windfall Lake gold deposit is currently one of the highest grade resource-stage gold projects in Canada. Mineralization occurs in four principal zones: Lynx, Zone 27, Caribou and Underdog. All zones comprise sub-vertical lenses following intrusive porphyry contacts plunging to the northeast. The deposit is well defined from surface to a depth of 900 metres and remains open along strike and at depth. Mineralization has been identified 30 metres from surface in some areas and as deep as 2,000 metres in others, with significant potential to extend mineralization down-plunge and at depth.

About Osisko Mining Inc.
Osisko is a mineral exploration company focused on the acquisition, exploration, and development of precious metal resource properties in Canada. Osisko holds a 100% interest in the high-grade Windfall Lake gold deposit located between Val-d'Or and Chibougamau in Québec and holds a 100% undivided interest in a large area of claims in the surrounding the Urban Barry area and nearby Quevillon area (over 3,300 square kilometres).

Cautionary Note Regarding Forward-Looking Information
This news release contains "forward-looking information" within the meaning of the applicable Canadian securities legislation that is based on expectations, estimates, projections and interpretations as at the date of this news release. The information in this news release about the Windfall Lake gold deposit being one of the highest grade resource-stage gold projects in Canada; the significance of results from the new infill drilling and ongoing drill definition and expansion program at the Windfall Lake gold project; the significance of assay results presented in this news release; the deposit remaining open along strike and at depth; potential depth extensions of the mineralized zones down-plunge and at depth; the actual mineralization of local visible gold; the current 800,000 metre drill program; the type of drilling included in the drill program; potential mineralization; the potential to extend mineralization up and down-plunge and at depth at the Windfall Lake gold deposit; the ability to realize upon any mineralization in a manner that is economic; the ability to complete any proposed exploration activities and the results of such activities, including the continuity or extension of any mineralization; and any other information herein that is not a historical fact may be "forward-looking information". Any statement that involves discussions with respect to predictions, expectations, interpretations, beliefs, plans, projections, objectives, assumptions, future events or performance (often but not always using phrases such as "expects", or "does not expect", "is expected", "interpreted", "management's view", "anticipates" or "does not anticipate", "plans", "budget", "scheduled", "forecasts", "estimates", "believes" or "intends" or variations of such words and phrases or stating that certain actions, events or results "may" or "could", "would", "might" or "will" be taken to occur or be achieved) are not statements of historical fact and may be forward-looking information and are intended to identify forward-looking information. This forward-looking information is based on reasonable assumptions and estimates of management of the Corporation at the time such assumptions and estimates were made, and involves known and unknown risks, uncertainties and other factors which may cause the actual results, performance or achievements of Osisko to be materially different from any future results, performance or achievements expressed or implied by such forward-looking information. Such factors include, among others, risks relating to the ability of exploration activities (including drill results) to accurately predict mineralization; errors in management's geological modelling; the ability of Osisko to complete further exploration activities, including drilling; property interests in the Windfall Lake gold project; the ability of the Corporation to obtain required approvals and complete transactions on terms announced; the results of exploration activities; risks relating to mining activities; the global economic climate; metal prices; dilution; environmental risks; and community and non-governmental actions. Although the forward-looking information contained in this news release is based upon what management believes, or believed at the time, to be reasonable assumptions. Osisko cannot assure shareholders and prospective purchasers of securities of the Corporation that actual results will be consistent with such forward-looking information, as there may be other factors that cause results not to be as anticipated, estimated or intended, and neither Osisko nor any other person assumes responsibility for the accuracy and completeness of any such forward-looking information, Osisko does not undertake, and assumes no obligation, to update or revise any such forward-looking statements or forward-looking information contained herein to reflect new events or circumstances, except as may be required by law.

For further information please contact:
John Burzynski
President and Chief Executive Officer
Telephone: (416) 363-8653