(MELBOURNE) OceanaGold Corporation (TSX: OGC) (ASX: OGC) (the “Company”) is pleased to provide its annual Resource and Reserve (“R&R”) statement for the year-ended 31 December 2020 and announce the filing of a Feasibility Study technical report prepared in accordance with National Instrument 43-101 for the Martha Underground Project within the Waihi District.

Highlights

• Increased Proven and Probable (“P&P”) Gold Reserves by 0.75 Moz, net of depletion, or 14% yearon-year to 143 Mt at 1.32 g/t Au for 6.06 Moz.
• Declared Initial P&P Gold Reserve at Martha Underground of 4.5 Mt at 4.33 g/t Au for 0.62 Moz in conjunction with the Feasibility Study.
• P&P Reserves of 40.8 Mt at 0.99 g/t Au for 1.3 Moz at Macraes, including 2.6 Mt at 2.10 g/t Au for 0.16 Moz at Golden Point Underground expected to deliver first production in the fourth quarter of 2021.
• Increased total Measured and Indicated (“M&I”) Gold Resources by 0.66 Moz, net of depletion, or 7% year-on-year to 243 Mt at 1.28 g/t Au for 10.0 Moz.
• Declared Inferred Gold Resources of 75 Mt at 1.8 g/t Au for 4.4 Moz, net of depletion, an increase of 2% year-on-year or 0.1 Moz.

Michael Holmes, President and CEO of OceanaGold said, ”We are pleased to declare gold Reserves of 6.06 Moz and 10.0 Moz of Measured and Indicated Resources, a 0.75 Moz increase in reserves net of depletion, reflecting our commitment to creating value through exploration, a quality asset base and consistent performance.”

“At the Waihi gold mine in New Zealand the Feasibility Study has defined an initial P&P Reserve of 0.62 Moz of gold for the Martha Underground Project, confirming our confidence in delivery of the asset and our vision for the Waihi District. Just North of Waihi, drilling is ongoing at the Wharekirauponga (“WKP”) Prospect to convert resources, test extensions to known mineralised veins and support the Pre-Feasibility study targeted for release in late 2021.”

“On the South Island of New Zealand, the Macraes life of mine has been extended to 2028 and the Golden Point Underground is on-track for first production later this year with an initial Reserve of 0.16 Moz of gold.”

“At the Haile gold mine in the United States of America, 2.43 Moz of gold Reserve is contained within the
optimised open pit while an important underground Reserve of 0.42 Moz is growing through conversion of a
large resource base totalling 0.53 Moz of Indicated Resource and 0.9 Moz of Inferred Resource. Exploration continues to focus on both continued resource conversion as well as underground discovery with the
objective to match production from the new underground mines with the open pit operations and ultimately extend gold production past the current life of mine of 2032.”

Reserves

As at 31 December 2020, the Company’s P&P Reserves stood at 143 Mt at 1.32 g/t Au for 6.06 Moz of gold, including 4.65 Moz of silver and 0.15 Mt of copper, representing a 0.75 Moz increase in gold Reserves yearon-year net of depletion (Table 1). The 14% year-on-year net increase is attributable to model updates of 1.00 Moz, reflecting the commitment to exploration drilling and organic growth as demonstrated by first-time reporting of 4.5 Mt at 4.33 g/t Au for 0.62 Moz Reserves at Martha Underground and 2.6 Mt at 2.10 g/t Au for 0.16 Moz at Golden Point Underground in New Zealand. Economic factors represent a minor contribution of 0.10 Moz to the net increase in P&P Reserves (Figure 1).

Resources

As at 31 December 2020, the Company’s M&I Resources stood at 243 Mt at 1.28 g/t Au for 10.0 Moz of gold, 14.0 Moz of silver and 0.17 Mt of copper (Table 2). On a consolidated basis, the Company increased M&I Resources by 0.66 Moz, year-on-year net of depletion, mainly due to the successful drilling-related resource upgrades of 0.65 Moz, predominantly at New Zealand operations. Changes in economic factors also had a positive impact of approximately 0.46 Moz (Figure 2).

Adjustments to M&I Resources include a net reduction of 0.18 Moz in 2020 that reflects a reduction at Macraes partially off-set by an addition at Waihi associated with operational changes, including:

• Macraes: reductions due to a proportion of Round Hill Open-pit resources that were excised immediate to the new Golden Point Underground and removal of non-economic Frasers Underground resources, and
• Waihi: additions due to a proportion of Martha Underground resource now reported within the Martha Open-pit.

Consolidated Inferred Resources, year-on-year, increased by 0.1 Moz to 4.4 Moz of gold, while silver and copper Inferred Resources also increased to 6.3 Moz and 0.04 Mt, respectively (Table 3, Figure 3).

Pricing and Sensitivities

The Company used gold prices of $1,500 per ounce and $1,700 per ounce for estimating P&P Reserves and Mineral Resources, respectively, and a silver price of $17.00 per ounce for estimating both Reserves and
Resources. The metal price assumptions used are aligned with the three-year trailing average gold and silver price actuals of $1,477 per ounce and $17.49 per ounce, respectively (2018 to 2020 year-end). The Company believes the three-year trailing average metals pricing most appropriately reflect the economic conditions at the time of mineral reserve estimation. The Company estimates a $1,300 gold price, a $200/oz decrease as compared to the current three-year trailing average utilised, would result in a reduction of approximately 4% in P&P Reserves.

New Zealand

Waihi

Reserves at Waihi stood at 0.63 Moz gold after reclassification of the Martha Open Pit reserve of 0.08 Moz. This 0.52 Moz increase year-on-year is due to the newly declared Martha Underground reserve of 4.5 Mt at
4.33 g/t Au for 0.62 Moz (Figure 4).

The Waihi M&I Resources stood at 1.83 Moz gold, representing a year-on-year increase of 0.39 Moz due primarily to the conversion of Inferred Resources at Martha Underground and model updates (see 16 February 2021 press release) and the addition of open pit resources at Martha and Gladstone (Figure 5). In 2021, the Company expects to drill 27,000 metres at Martha Underground with a focus on resource conversion (20,000 metres) and resource extension (7,000 metres). The Company has revised the Exploration Target for Martha Underground which now stands at 5 to 7 million tonnes with a grade of 4.0 to
5.0 g/t gold. It is important to note that the Exploration Target is exclusive of the reported Mineral Resources and relates to the portion of the deposit that has not yet been adequately drill tested (see cautionary statement below).

Cautionary Statement: The Exploration Target is based on the assessment of surface and underground drill data collected by the Company in addition to the significant amount of historical and archived geological and mine data from over a century of mining activity at Waihi. The Exploration Target is conceptual in nature and insufficient exploration has been undertaken in the areas that the Exploration Target relates to estimate a Mineral Resource. It is uncertain if further exploration will result in the estimation of a Mineral Resource.

The Waihi Inferred Resources stood at 1.4 Moz gold. This represents a 0.1 Moz increase due to the expansion of the Martha Open Pit resource (Figure 6).

At the WKP project located 10 kilometres north of the existing Waihi facilities, the Company reported an Indicated Resource of 1.0 Mt at 13.4 g/t Au and 25.5 g/t Ag for 0.42 Moz of gold and 0.80 Moz of silver, in addition to an Inferred Resource of 1.9 Mt at 12 g/t Au and 20 g/t Ag for 0.72 Moz of gold and 1.23 Moz of silver, as reported in the 2019 Resource and Reserve Statement. These estimates remain unchanged in the
current R&R statement. The Company intends to incorporate 2020 (4,000 metres) and 2021 drilling (estimated 10,500 metres) into an updated resource model supporting the completion of a Pre-Feasibility study by 2021 year-end.

Macraes

The P&P Reserves for Macraes stood at 1.30 Moz gold with 1.08 Moz in the open pits and 0.22 Moz of gold in the Frasers and Golden Point underground mines (Figure 7). Year-on-year drilling-related reserve growth has increased Reserves 0.20 Moz net of 2020 depletion due mainly to the addition of 0.17 Moz at Golden Point Underground and reserve growth at Frasers Open Pit.

The Macraes M&I Resources stood at 3.60 Moz of gold, including 0.56 Moz for the Frasers Underground and Golden Point Underground mines (Figure 8). The year-on-year net increase in M&I Resources of 0.15 Moz is attributable to model updates of 0.40 Moz, reflecting successful exploration drill programs as demonstrated by first-time reporting of the Golden Point Underground resource (10 September 2020), open pit resource growth and to a lesser extent, 0.14 Moz reflected in economic factors. Adjustments reflect Round Hill Open Pit reductions due to a loss of resources associated with the allocation to Golden Point Underground and removal of non-economic Frasers Underground resources (see Figure 8).

Macraes Inferred Resources stood at 0.8 Moz of gold, a decrease from the previous year, due mainly to the conversion of Inferred Resources to the Indicated category and, to a lesser extent, depletion (Figure 9).

Reefton

Resources for the Blackwater Project remain on the Company’s inventory and are unchanged from the 31 December 2019 reported resources.

United States of America

Haile

P&P Reserves totalled 2.84 Moz of gold including 0.42 Moz in the Haile Underground (Figure 10). Depletion has largely been offset by resource conversion and changes in economic factors.

Total Haile M&I Resources stood at 3.18 Moz of gold, including 0.53 Moz for the Haile Underground. Depletion during 2020 has been offset by economic factors (Figure 11).

Year-on-year, Inferred Resources remain essentially unchanged with resource update reductions being offset by changes in economic factors (Figure 12). Haile growth focuses on resource conversion drilling and exploration of underground targets.

Philippines

Didipio

Didipio P&P Reserves stood at 1.28 Moz of gold, 2.7 Moz of silver and 0.15 Mt of copper, a small year-on-year increase (Figure 13). The increase is largely due to a lowered reserve reporting cut-off grade (0.76 g/t
AuEq cut-off) in areas adjacent to development planned to access higher grade stoping areas (1.16 g/t AuEq cut-off). The reserves include 23 Mt of low and medium grade open pit stockpiles, 5.3 Mt of which are based upon a 0.27 g/t AuEq cut-off, the remainder based on an approximate 0.4 g/t AuEq cut-off. The Company continues to work with the Philippine National Government on renewal of Didipio’s operating agreement (the Financial or Technical Assistance Agreement or “FTAA”), and the mine remains in a state of operational standby. As the renewal discussion is continuing to progress and detailed planning and consultation is underway for recommencement of operation, the Company maintains reporting of Didipio as a Mineral Reserve.

Didipio M&I Resources stood at 1.43 Moz of gold, 2.93 Moz of silver and 0.17 Mt of copper, a small year-on-year increase of 0.05 Moz due to lowered resource reporting cut-off grade (0.67 g/t AuEq cut-off at increased gold price of $1,700 per ounce) (Figure 14). The resources include 23 Mt of low and medium grade open pit stockpiles.

Inferred Resources stood at 0.4 Moz of gold, 0.6 Moz of silver and 0.04 Mt of copper, a 0.1 Moz year-on-year increase due to lowered cut-off grade (Figure 15).

Other

OceanaGold’s interest in the Sam’s Creek project in New Zealand remains unchanged at 20%.

As part of the requirements under the listing rules of the Australian Stock Exchange, the Company has filed a separate document containing the material summaries and JORC Table 1 information related to the resource and reserves. These can be found at https://oceanagold.com/investor-centre/tsx-asx-filings/.

Martha Underground Feasibility Study

The Waihi District – Martha Underground Feasibility Study, 31 March 2021, provides an update of information contained in the Waihi District PEA, 30 August 2020 for all Waihi geological resources and for mining evaluations for Martha Underground. The Feasibility Study includes an initial Reserve at Martha Underground of 4.5 Mt at 4.33 g/t Au for 0.62 Moz. The Feasibility Study also includes reporting of an additional 0.26 Moz of Indicated Resource at Martha Underground that has for the most part been converted from Inferred Resource (see comparison of the resources in Tables 5 and 6 below). Correspondingly, this conversion has resulted in a 0.20 Moz decrease in Inferred Resources.

Source: OceanaGold