Osisko Lynx Infill Drilling Continues to Return High Grades

TORONTO, March 21, 2019 - Osisko Mining Inc. (OSK:TSX. "Osisko" or the "Corporation") is pleased to provide new infill drilling results from its 100% owned Windfall gold project located in the Abitibi greenstone belt, Urban Township, Eeyou Istchee James Bay, Québec. The new results are from the general area being considered for the planned bulk sample in the Lynx deposit. A closely spaced infill drill program (approximately 10 metres x 10 metres) has been designed to increase the geological control and grade definition to further test and select the location for the bulk test. The definition program is in progress, and the location of the Lynx bulk sample will be chosen on completion of the program in the coming months. Highlights include:

224 g/t Au over 2.8 metres and
77.9 g/t Au over 2.1 metres in OSK-W-18-1804;
51.2 g/t Au over 3.2 metres in OSK-W-18-1812;
43.7 g/t Au over 3.2 metres in OSK-W-19-1850;
56.0 g/t Au over 2.2 metres in OSK-W-19-1865;
38.6 g/t Au over 2.2 metres in OSK-W-19-1855;
32.6 g/t Au over 2.4 metres in OSK-W-18-1811;
18.0 g/t Au over 4.7 metres in OSK-W-18-1807; and
28.6 g/t Au over 2.3 metres in OSK-W-19-1860.

Maps showing hole locations, and full analytical results are available at www.osiskomining.com. Significant new analytical results from 19 intercepts in 11 drill holes are presented below.

Note: True widths are estimated at 65 – 80% of the reported core length interval. See "Quality Control and Reporting Protocols" below.

OSK-W-18-1804 intersected three intervals: 224 g/t Au over 2.8 metres, 10.8 g/t Au over 4.1 metres and 77.9 g/t Au over 2.1 metres. The first interval contains pyrite-tourmaline stringers with local visible gold, 5% pyrite clusters, and trace pyrite stringers in a fragmental rhyolite with moderate to strong silica alteration. The second interval contains 3% disseminated pyrite and trace sphalerite in pervasive silica flooding, trace pyrite-tourmaline stringers and 1% disseminated pyrite in a strongly silicified rhyolite. The third interval contains up to 2% pyrite stringers, trace disseminated pyrite and clusters, and trace pyrite in tourmaline ptygmatic veins in a chloritized and slightly sericitized gabbro.

OSK-W-18-1807 intersected two intervals: 3.14 g/t Au over 2.3 metres and 18.0 g/t Au over 4.7 metres. The first interval contains 3% pyrite with pervasive silica flooding and tourmaline ptygmatic and quartz-tourmaline veins and 1% pyrite-tourmaline stringers in alternating silicified and sericitized fragmental intrusions, rhyolites and porphyritic felsic dikes. The second interval contains 35% semi massive pyrite with pervasive silica flooding in a strongly silicified and a weakly fuchsite and sericite altered porphyritic felsic dike.

OSK-W-18-1809 intersected two intervals: 3.40 g/t Au over 2.0 metres and 6.13 g/t Au over 2.3 metres. The first interval contains up to 4% pyrite clusters in pervasive silica flooding in a silicified and sericitized fragmental felsic dike. The second interval contains trace pyrite in pervasive silica flooding and trace pyrite-tourmaline stringers with local visible gold in pervasive silica flooding with fuchsite hosted in a sericitized and silicified rhyolite.

OSK-W-18-1811 intersected four intervals: 4.10 g/t Au over 2.4 metres, 5.56 g/t Au over 2.4 metres, 15.2 g/t Au over 2.0 metres and 32.6 g/t Au over 2.4 metres. The first interval contains of 5% pyrite clusters and 4% disseminated pyrite in a moderate sericite and weak silica altered dacite. The second interval contains trace pyrite-tourmaline stringers, and pyrite-tourmaline veins in a moderate chlorite and weak sericite and silica altered gabbro. The third interval contains 8% disseminated pyrite in clusters or fracture filling, trace chalcopyrite in quartz-tourmaline veins, and 1% pyrite-tourmaline stringers in a bleached and sericitized andesite. The fourth interval contains up to 15% pyrite stringers and 5% disseminated pyrite in silica flooding within a moderately sericitized porphyritic felsic dike.

OSK-W-18-1812 intersected 51.2 g/t Au over 3.2 metres. Mineralization consists of local visible gold, up to 15% pyrite and trace sphalerite associated within pervasive silica flooding, moderate fuchsite and moderate sericite altered rhyolite.

OSK-W-19-1846 intersected 11.3 g/t Au over 3.1 metres. Mineralization consists of local visible gold, up to 15% pyrite stringers with pyrite-silica flooding hosted in strong silica, moderate sericite and weak fuchsite altered rhyolite.

OSK-W-19-1850 intersected 43.7 g/t Au over 3.2 metres. Mineralization consists of local visible gold, up to 15% disseminated pyrite and stringers, 5% disseminated sphalerite and pyrite-tourmaline stringers hosted in a strong silica and fuchsite altered rhyolite.

OSK-W-19-1852 intersected 14.8 g/t Au over 2.6 metres. Mineralization consists of local visible gold, up to 7% pyrite clusters and stringers with pervasive silica flooding hosted in a strong silica, moderate sericite, fuchsite and carbonates altered rhyolite.

OSK-W-19-1855 intersected 38.6 g/t Au over 2.2 metres and 6.04 g/t Au over 3.3 metres. The first interval contains local visible gold and 1% pyrite stringers hosted in a strong silica altered fragmental felsic intrusion. The second interval contains 1% disseminated pyrite with quartz-tourmaline veins hosted in a weak sericite and silica altered fragmental felsic intrusion.

OSK-W-19-1860 intersected 28.6 g/t Au over 2.3 metres. Mineralization consists of local visible gold, 1% pyrite stringers, and up to 5% disseminated pyrite within a bleached and fuchsite altered fragmental felsic intrusion.

OSK-W-19-1865 intersected 56.0 g/t Au over 2.2 metres. Mineralization consists of local visible gold, 6% disseminated pyrite, and 1% sphalerite and ptygmatic tourmaline stringers within a strong silica and fuchsite altered porphyritic felsic intrusion.

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