Osisko Mining Inc. (TSX:OSK) is pleased to provide new drilling results from the ongoing definition and expansion drill 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 focused on infill drilling and expansion drilling at the Lynx deposit, exploration on the main mineralized zones, and deep exploration in the central areas of the mineralized intrusive system. Twenty-one drills are active at Lynx and Triple Lynx, with another three drills conducting infill and exploration drilling on other areas of the deposit.

Infill drilling at Lynx Extension has returned one of the highest-grade intervals intersected a Windfall to date, returning 106 g/t Au over 13.0 metres in OSK-W-19-991-W8. A second infill hole in the Lynx Extension (OSK-W-19-1857-W8) returned 62.4 g/t over 5.7 metres. The infill holes from the 50-metre spacing definition program continue to confirm the continuity of the Lynx Extension zone 315 metres down plunge of the nearest resource wireframe (see Osisko news releases dated June 3, 2019, April 16, 2019 and November 27, 2018). The Lynx Extension remains open down plunge, and definition drilling will continue in the open areas.

Osisko President and Chief Executive Officer John Burzynski commented: “Lynx continues to deliver strong results and is underpinning the high-grade potential of the Windfall deposit. Infill drilling in Lynx Extension is adding good connectivity and meaningful ounces, which should have a positive effect on the upcoming resource update.  Exploration is pursuing the down plunge areas of the Lynx zones, all of which remain open at depth.”

Maps and sections showing hole locations and full analytical results are available at www.osiskomining.com.

Notes: True widths are estimated at 55 – 80% of the reported core length interval. See “Quality Control and Reporting Protocols” below. Ext = Extension.

Drill hole location

OSK-W-19-991-W8 intersected 106 g/t Au over 13.0 metres. Mineralization contains local visible gold and electrum, up to 7% pyrite clusters, and local chalcopyrite, sphalerite and galena hosted in a bleached, fuchsite and silica altered gabbro.

OSK-W-19-1857-W8 intersected 62.4 g/t Au over 5.7 metres. Mineralization contains local visible gold and native silver, up to 10% disseminated pyrite and local chalcopyrite associated with strong pyrite-silica flooding hosted in a strong silica, sericite and fuchsite altered gabbro.

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 55-80% 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 Quévillon area (over 2,700 square kilometres).