Osisko Infills New High Grade at Lynx

TORONTO, May 30, 2019 - Osisko Mining Corp. 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 includes 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 52 intercepts in 15 drill holes and 9 wedges focused on infill drilling from surface and underground are presented below.

Osisko President and Chief Executive Officer John Burzynski commented: "Our infill drill program at Windfall continues to give us confidence that we will see strong results when we table our next resource estimate later this year. We are having great success at the drill bit, particularly from the Lynx Zone which remains open to depth with excellent grades. Day-by-day our exploration team is growing the Windfall deposit, confirming our belief that we are onto a world-class high-grade system."

Highlights from new infill drilling results include: 96.7 g/t Au over 4.8 metres in OSK-W-19-1891; 189 g/t Au over 2.4 metres in OSK-W-19-1831; 86.9 g/t Au over 3.7 metres in OSK-W-18-1477; 75.8 g/t Au over 4.0 metres in OSK-W-19-1181-W7; 37.6 g/t Au over 7.8 metres in OSK-W-17-934-W4; 105 g/t Au over 2.2 metres in OSK-W-18-1477 and 26.0 g/t Au over 7.9 metres in OSK-W-19-1414-W8. Maps showing hole locations and full analytical results are available at www.osiskomining.com.

OSK-W-18-1477 intersected nine mineralized intervals in Lynx: 3.09 g/t Au over 3.0 metres, 86.9 g/t Au over 3.7 metres, 105 g/t Au over 2.2 metres, 3.82 g/t Au over 2.0 metres, 15.9 g/t Au over 2.0 metres, 7.01g/t Au over 2.8 metres, 8.83 g/t Au over 2.0 metres, 4.83 g/t Au over 11.8 metres and 20.3 g/t Au over 2.2 metres. The first interval is composed of 20% pyrite clusters with tourmaline in a strongly altered fuchsite gabbro. The second interval is composed of trace and up to 5% pyrite ± tourmaline stringers with local visible gold, 5% pyrite in ptygmatic tourmaline veins, 5% smoky quartz veins with 25% pyrite and trace chalcopyrite and sphalerite at the contact between a silica altered porphyritic felsic dike and a sericite altered rhyolite. The third to eighth intervals contain local visible gold, up to 1% pyrite stringers and clusters and up to 5% disseminated pyrite in pervasive silica flooding hosted in a rhyolite with weak sericite and silica alteration and moderate chlorite alteration. The last interval is composed of 3% pyrite in quartz-tourmaline veins and 2% disseminated pyrite in a moderate sericite, chlorite and weak fuchsite altered andesite.

OSK-W-18-1608 intersected four intervals in Lynx: 3.74 g/t Au over 3.0 metres, 3.50 g/t Au over 5.5 metres, 3.73 g/t Au over 5.6 metres and 6.61 g/t Au over 2.0 metres. Mineralization in all four intervals is composed of up to 5% interstitial pyrite, 2% pyrite stringers, and trace sphalerite with local quartz-tourmaline veins in a moderate silica and weak sericite altered rhyolite.

OSK-W-18-1711-W2 intersected 4.15 g/t Au over 5.4 metres in Lynx. Mineralization is composed of 7% pyrite in fracture filling with pervasive silica flooding and 2% sphalerite in a moderate silica altered porphyritic felsic dike.

OSK-W-19-934-W4 intersected three intervals in Lynx: 37.6 g/t Au over 7.8 metres, 7.24 g/t Au over 2.0 metres, and 20.6 g/t Au over 2.0 metres. The first and second intervals are composed of 8% disseminated pyrite, 3% sphalerite associated with pervasive silica flooding and ptygmatic tourmaline vein, 5% pyrite stringers, and 4% pyrite in smoky veinlets hosted in a weak fuchsite altered gabbro and weak silica altered rhyolite. The third interval is composed of 1% pyrite stringers in a moderate chlorite and weak sericite altered rhyolite.

OSK-W-19-1181-W6 intersected 10.0 g/t Au over 2.3 metres and 13.4 g/t au over 2.0 metres in Lynx. The first interval is composed of 4% stringer and clustered pyrite and 10% quartz-tourmaline veins in a moderate chlorite and weak sericite altered gabbro. The second interval is composed of trace pyrite clusters with pervasive silica flooding in a moderate sericite and weak silica altered rhyolite.

OSK-W-19-1181-W7 intersected three intervals in Lynx: 5.52 g/t Au over 2.0 metres, 75.8 g/t Au over 4.0 metres and 61.1 g/t Au over 2.4 metres. The first interval is composed of 4% disseminated and stringer pyrite and 40% quartz-tourmaline veins in a moderate sericite-fuchsite and weak silica altered gabbro. The second interval contains local visible gold, up to 10% pyrite in smoky quartz-veins, 20% disseminated, clustered and stringer pyrite, 2% pyrite with ptygmatic tourmaline veins hosted in a silicified rhyolite, a sericitized porphyritic felsic dike and a sericite-fuchsite altered gabbro.The third interval is composed of local visible gold, 25% pyrite with smoky veins, up to 10% pyrite stringers, 2% pyrite in quartz-carbonates veins, and 15% disseminated, clustered or interstitial pyrite in a strong silica and moderate sericite-chlorite-fuchsite altered gabbro.

OSK-W-19-1414-W8 intersected 26.0 g/t Au over 7.9 metres in Lynx. Mineralization is composed of 5% pyrite stringers and 3% pyrite clusters within a felsic dike and rhyolite. Both have moderate fuchsite alteration.

OSK-W-18-1808 intersected 6.69 g/t Au over 2.1 metres in Zone 27. Mineralization is composed of two 20 centimetre-wide intervals containing up to 5% pyrite-tourmaline stringers and 2% disseminated pyrite at the contact between a sericitized and silicified porphyritic felsic dike and a rhyolite.

OSK-W-19-1831 intersected 189 g/t Au over 2.40 metres in Lynx. Mineralization is composed of local visible gold in fracture filling, 8% pyrite stringers and clusters in a fuchsite altered gabbro injected by multiple quartz-tourmaline veins.

OSK-W-19-1835 intersect 12.8 g/t Au over 2.4 metres in Underdog. Mineralization is composed of up to 20% disseminated and stringer pyrite at the contact between two porphyritic felsic intrusion with weak sericite and silica alteration.

OSK-W-19-1835-W2 intersected 19.8 g/t Au over 2.0 metres and 5.06 g/t Au over 2.3 metres in Underdog. The first interval is composed of 1% chalcopyrite stringers in a strong silica and moderate sericite altered porphyritic felsic dike. The second interval is composed of 3% pyrite stringers in a moderate sericite altered porphyritic felsic dike.

OSK-W-19-1847 intersected 4.95 g/t Au over 2.3 metres in Lynx. Mineralization is composed of 5% pyrite in pervasive silica flooding in a strong sericite and moderate silica altered and sheared rhyolite at the contact with a chloritized gabbro.

OSK-W-19-1886 intersected 5.0 g/t Au over 2.4 metres in Caribou. Mineralization is composed of 1% disseminated and stringer pyrite within a weak silica and sericite altered rhyolite.

OSK-W-19-1891 intersected three intervals in Lynx: 72.3 g/t Au over 2.3 metres, 96.7 g/t Au over 4.8 metres and 70.0 g/t Au over 2.4 metres. Mineralization in all three intervals contains local visible gold disseminated in fracture filling, up to 7% pyrite and 1% chalcopyrite associated with smoky quartz veins, up to 10% disseminated pyrite, 5% stringer and clustered pyrite, and 1% disseminated chalcopyrite associated with dismembered quartz-carbonate veins. Mineralization is hosted in a moderate sericite-silica and fuchsite altered gabbro and a moderate sericite-chlorite-fuchsite altered rhyolite.

OSK-W-19-1891-W1 intersected four intervals in Lynx: 7.49 g/t Au over 2.0 metres, 4.04 g/t Au over 4.3 metres, 31.1 g/t Au over 2.0 metres and 17.0 g/t Au over 6.4 metres. The first interval is composed of 3% pyrite clusters hosted in a weakly silicified and sericitized brecciated rhyolite with moderate ankerite and chlorite alteration. The second interval is composed of up to 10% disseminated, clustered, and stringer pyrite associated with quartz-carbonate ± tourmaline veins hosted in a moderate fuchsite altered gabbro and a moderate sericite altered rhyolite. The third interval is composed of 1% pyrite stringers in a sericitized rhyolite. The fourth interval consists of 5% disseminated, clustered, and stringer pyrite in pervasive silica flooding hosted in a strongly sericitized rhyolite crosscut by gabbro dikes.

OSK-W-19-1891-W2 intersected 5.18 g/t Au over 2.7 metres in Lynx. Mineralization is composed 10% disseminated, clustered, and stringer pyrite associated with a quartz-carbonate vein and a smoky quartz vein hosted in a weak fuchsite altered gabbro with moderate silica and sericite alteration.

OSK-W-19-1891-W3 intersected three intervals in Lynx: 7.54 g/t Au over 4.7 metres, 10.6 g/t Au over 2.3 metres and 4.99 g/t Au over 2.0 metres. The first interval is composed of 5% pyrite-tourmaline clusters and 1% pyrite-tourmaline stringers associated with pervasive silica flooding hosted at the contact between a strong sericite-silica altered gabbro and a moderate sericite altered rhyolite. The second interval contains local visible gold and up to 20% pyrite associated with smoky quartz-tourmaline veins hosted in a strong but patchy silicified and sericitized rhyolite. The third interval is composed 3% pyrite in quartz-carbonate veins in a strongly sericitized and moderately chloritized rhyolite.

OSK-W-19-1898 intersected three intervals in Caribou: 4.85 g/t Au over 2.2 metres, 5.26 g/t Au over 4.6 metres and 6.49 g/t Au over 4.6 metres. The first interval is composed of 1% pyrite stringers, 2% pyrite in stockwork, and 20% quartz-tourmaline veins in a moderate silica and sericite altered rhyolite. The second and third intervals are composed of up 10% pyrite stringers in a moderate sericite and silica altered rhyolite.

OSK-W-19-1904 intersected 51.9 g/t Au over 2.1 metres in Caribou. Mineralization includes local visible gold and 2% pyrite stringers hosted in a moderately sericitized and silicified porphyritic felsic dike.

OSK-W-19-1915 intersected two intervals in Lynx: 3.25 g/t Au over 2.7 metres and 3.12 g/t Au over 2.5 metres. The first interval is composed of 1% pyrite clusters and trace chalcopyrite in a weak sericite altered andesite. The second interval is composed of trace disseminated pyrite in a weak silica-fuchsite altered andesite with moderate sericite and chlorite alteration.

WST-19-0062 intersected 18.2 g/t Au over 2.2 metres in Zone 27. Mineralization consists of 2% pyrite clusters and 1% quartz-tourmaline veins within a moderate sericite, chlorite and weak fuchsite altered gabbro. WST-18-0062 was drilled from underground drill station BM-150-960-S located 150 metres below surface on section 2175E.

WST-19-0083 intersected 32.9 g/t Au over 2.6 metres in Zone 27. Mineralization includes 2% pyrite stringers associated with a quartz-tourmaline vein and 1% disseminated pyrite hosted in a moderate sericite and weak silica altered porphyritic felsic dike. WST-18-0083 was drilled from underground drill station AN-190-155-N located 190 metres below surface on section 2300E.

WST-19-0085 intersected 5.73 g/t Au over 2.1 metres in Caribou. Mineralization is composed of 1% pyrite clusters in quartz-tourmaline veins hosted in a moderate sericite and weak silica altered porphyritic felsic dike. WST-19-0085 was drilled from underground drill station AN-190-155-N located 190 metres below surface on section 2300E.

WST-19-0088 intersected 4.37 g/t Au over 2.6 metres and 6.28 g/t Au over 2.8 metres in Zone 27. The first interval is composed of 4% disseminated, clustered, and stringer pyrite in a moderate chlorite altered and fragmental andesite. The second interval is composed of 3% disseminated and clustered pyrite, and 1% pyrite stringers in a brecciated, tourmaline-rich fragmental andesite. WST-19-0088 was drilled from underground drill station AN-190-155-N located 190 metres below surface on section 2300E.

Qualified Person
The scientific and technical information in 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 Ltd. 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 (2,700 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 the ongoing definition and expansion drilling at the Windfall Lake gold project; the significance of drill results, intersections and assays presented in this news release; Osisko's timing and ability to prepare an updated resource estimate; the results of the updated resource estimate (if any); the continued growth of the Windfall deposit; the deposit remaining open along strike and at depth; the Lynx Zone remaining open to depth with excellent grades; potential depth extensions of the mineralized zones down-plunge and at depth; the actual mineralization of local visible gold; 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, Tel: (416) 363-8653