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OceanaGold Continues to Delineate High-Grade Mineralization in the Haile Underground

Drill Results

September 11, 2024

News Release

OceanaGold Continues to Delineate High-Grade Mineralization in the

Haile Underground

(VANCOUVER) OceanaGold Corporation (TSX: OGC; OTCQX:OCANF) (“OceanaGold” or the “Company”)

is pleased to provide results from exploration and resource conversion drilling at the Haile Gold Mine

(“Haile”) in the United States.

Gerard Bond, President & CEO of OceanaGold, said “ Today’s outstanding resource conversion and

definition drill results support our goal of delineating 2 million ounces underground at Haile by the end of

this year. Infill drill results at Ledbetter Phase 4 are exceptional in width and grade and inform the work

evaluating whether to mine the last phase of Ledbetter from underground. Additionally, new r esource

conversion results announced today improve our confidence in Horseshoe mineralization at depth, and

results from Horseshoe Extension have intersected new mineralization proximal to existing infrastructure.”

Drill highlights include (core length):

• 82.0 m @ 35.07 g/t Au Ledbetter Phase 4 (DDH1218 – conversion)

• 4.6 m @ 398.12 g/t Au, Ledbetter Phase 4 (DDH1228 – conversion)

• 71.0 m @ 16.80 g/t Au Ledbetter Phase 4 (DDH1220 – conversion)

• 45.3 m @ 21.29 g/t Au, Ledbetter Phase 4 (DDH1226 – conversion)

• 29.0 m @ 33.11 g/t Au, Ledbetter Phase 4 (DDH1230 – conversion)

• 54.4 m @ 14.82 g/t Au, Ledbetter Phase 4 (DDH1237 – conversion)

• 42.7 m @ 15.55 g/t Au, Ledbetter Phase 4 (DDH1246 – conversion)

• 48.5 m @ 8.30 g/t Au, Ledbetter Phase 4 (DDH1232 – conversion)

• 40.5 m @ 13.30 g/t Au, Horseshoe (UGD0029 - conversion)

• 16.6 m @ 9.00 g/t Au and 8.4 m @ 5.06 g/t Au, Horseshoe (UGD0030 - conversion)

• 11.6 m @ 4.05 g/t Au, Horseshoe Extension (UGD0055 – definition)

Results announced today can be viewed in 3D using VRIFY at the following link1:

https://vrify.com/meetings/recordings/f7d13714-449f-4cd1-a6c0-935c31100911

1Note: Drill results reflect those set forth in OceanaGold’s press release dated September 11, 2024 and do not include all his torical

drill results. For further information relating to drill holes highlighted, please see the press release.

Ledbetter Phase 4

Ledbetter Phase 4 mineralization sits within the open pit reserve (Figure 1) and is currently in the mine plan

as the final Ledbetter open pit phase. With a higher -grade resource at Ledbetter Phase 4 potentially

sufficient to support an underground mine with improved economics, trade- off study work is underway to

confirm the future preferred mining option. To support this study work, a resource conversion drill program

is underway to improve confidence and provide drill core for metallurgical testing (Figure 1). A total of 9,053

metres and 24 holes have been completed, with highlights including 82.0 m @ 35.07 g/t Au from DDH1218,

4.6 m @ 398.12 g/t Au from DDH1228, and 71.0 m @ 16.80 g/t Au from DDH1220. These drill results have

exceeded expectations compared to previous drilling outcomes.

An additional ~2,850 metres and 5 holes are being drilled in the remaining months of 2024 to test

mineralization, approximately 50 to 250 metres to the northwest of the current Ledbetter Phase 4 resource

(Figure 1).

Figure 1: Ledbetter Phase 4 mineralization and recent drill holes annotated.

Horseshoe and Horseshoe Extension (HEX)

Resource conversion and definition drilling undertaken from the Horseshoe Underground mine continues

with 6,956 metres completed of a planned 10,605 metres this year. The results from 15 new drill holes have

been received, with 3 holes supporting resource conversion of Inferred resources and 12 holes supporting

resource definition of the HEX target. HEX is not currently a resource, however drilling is ongoing to test its

potential as it is adjacent to the current Horseshoe Underground mine and within 150 metres of the planned

decline to access Palomino Underground.

The latest drilling of Horseshoe has targeted Inferred resources in the l ower zone with 3 holes all

intersecting mineralization and delivering results in line with expectations based on the resource model .

Highlights from Horseshoe include 40.5 m @ 13.30 g/t Au including 9.7 m @ 46.79 g/t Au (UGD0029) and

16.6 m @ 9.00 g/t Au (UGD0030) and 21.1 m @ 2.74 g/t Au (UGD0027).

Following the significant drill results reported in our April 3, 2024 press release, the latest drilling at HEX

has targeted 3 zones of minerali zation: upper, middle, and lower HEX. Drilling has (i) further defined

continuity in the upper zone with 3 holes (UGD0046, 52, 54), (ii) defined continuity of the middle zone with

4 holes (UGD0053, 55, 56, 57), and (iii) stepped out on the lower minerali zed zone to test extensions with

5 holes (UGD0037, 48, 49, 50, 51). Significantly, hole UGD0050 has intercepted mineralization of 24.2 m

@ 2.47 g/t Au ~30 metres below the currently defined lower zone of mineralization (Figure 2). In addition,

significant results were returned from UGD0046 with 13.7 m @ 3. 42 g/t Au in the upper zone, and from

UGD0055 with 11.6 m @ 4.05 g/t and UGD0056 with 27.2 m @ 1.45 g/t Au from the middle zone.

Drilling is ongoing at HEX for the remainder of 2024 with the goal to define an initial resource estimate in

Q1 2025.

Figure 2: Schematic long section (looking north-west) showing Horseshoe and Horseshoe

Extension mineralization and recent drill holes annotated.

Table 1: Haile drill intersections.

Hole ID From To

Interval Au Target Category

(m) (m) (m) (g/t)

DDH1217 258.7 264.8 6.1 2.58 Ledbetter 04 Conversion

DDH1218 206.6 247.4 39.3 2.53 Ledbetter 04 Conversion

And 284.7 366.6 82.0 35.07 Ledbetter 04 Conversion

Including 295.0 299.5 4.5 521.79 Ledbetter 04 Conversion

And including 337.7 340.7 3.1 74.08 Ledbetter 04 Conversion

DDH1219 197.5 219.4 22.0 2.45 Ledbetter 04 Conversion

And 304.2 309.9 5.7 43.16 Ledbetter 04 Conversion

Including 304.2 306.6 2.4 95.10 Ledbetter 04 Conversion

And 344.4 364.1 19.7 14.17 Ledbetter 04 Conversion

Including 348.7 350.5 1.8 113.00 Ledbetter 04 Conversion

DDH1220 201.2 240.9 39.7 2.99 Ledbetter 04 Conversion

And 291.6 362.6 71.0 16.80 Ledbetter 04 Conversion

Including 301.6 309.3 7.6 106.28 Ledbetter 04 Conversion

DDH1221 258.0 271.0 13.0 1.56 Ledbetter 04 Conversion

DDH1224 217.6 223.9 6.3 2.97 Ledbetter 04 Conversion

And 235.2 238.2 3.0 7.62 Ledbetter 04 Conversion

And 324.4 344.5 19.7 7.47 Ledbetter 04 Conversion

Including 327.0 329.0 2.0 41.13 Ledbetter 04 Conversion

DDH1225 299.7 306.5 6.8 2.29 Ledbetter 04 Conversion

And 315.0 368.8 53.8 6.35 Ledbetter 04 Conversion

Including 321.4 325.4 4.0 43.12 Ledbetter 04 Conversion

DDH1226 197.1 207.5 10.4 5.25 Ledbetter 04 Conversion

And 290.5 304.5 14.0 4.15 Ledbetter 04 Conversion

And 314.9 360.2 45.3 21.29 Ledbetter 04 Conversion

Including 316.4 319.4 3.1 275.08 Ledbetter 04 Conversion

DDH1228 239.0 246.3 7.3 4.99 Ledbetter 04 Conversion

Including 239.0 240.2 1.2 20.90 Ledbetter 04 Conversion

And 299.7 304.2 4.6 398.12 Ledbetter 04 Conversion

Including 299.7 301.2 1.5 1120.00 Ledbetter 04 Conversion

And 318.6 331.4 12.8 3.78 Ledbetter 04 Conversion

And 338.9 362.8 23.8 5.76 Ledbetter 04 Conversion

DDH1229 353.3 360.5 7.2 2.02 Ledbetter 04 Conversion

DDH1230 193.3 195.7 2.4 12.27 Ledbetter 04 Conversion

And 202.3 231.3 29.0 33.11 Ledbetter 04 Conversion

Including 222.4 227.8 5.5 141.99 Ledbetter 04 Conversion

And 291.9 295.5 3.6 5.54 Ledbetter 04 Conversion

And 306.4 309.3 2.9 6.71 Ledbetter 04 Conversion

And 347.5 365.4 17.9 5.85 Ledbetter 04 Conversion

DDH1231 NSR Ledbetter 04 Conversion

Hole ID From To

Interval Au Target Category

(m) (m) (m) (g/t)

DDH1232 357.4 405.9 48.5 8.30 Ledbetter 04 Conversion

DDH1233 342.6 350.2 7.6 2.45 Ledbetter 04 Conversion

DDH1234 185.3 203.9 18.6 6.09 Ledbetter 04 Conversion

And 211.9 217.2 5.3 20.17 Ledbetter 04 Conversion

And 284.1 286.3 2.2 24.80 Ledbetter 04 Conversion

And 307.0 322.9 15.8 6.96 Ledbetter 04 Conversion

And 336.3 358.5 22.2 5.89 Ledbetter 04 Conversion

DDH1235 343.3 357.4 14.1 2.40 Ledbetter 04 Conversion

DDH1236 343.4 353.3 9.9 1.89 Ledbetter 04 Conversion

DDH1237 189.3 193.6 4.3 22.42 Ledbetter 04 Conversion

And 202.2 210.1 7.9 20.78 Ledbetter 04 Conversion

Including 204.1 207.0 2.9 49.36 Ledbetter 04 Conversion

And 217.0 220.7 3.8 3.55 Ledbetter 04 Conversion

And 283.2 292.4 9.1 10.69 Ledbetter 04 Conversion

And 301.5 355.9 54.4 14.82 Ledbetter 04 Conversion

Including 310.7 312.2 1.5 331.00 Ledbetter 04 Conversion

Including 318.0 319.2 1.2 26.40 Ledbetter 04 Conversion

DDH1238 363.7 398.4 34.7 2.90 Ledbetter 04 Conversion

DDH1239 320.2 327.0 6.8 3.93 Ledbetter 04 Conversion

DDH1240 270.4 278.7 8.3 2.06 Ledbetter 04 Conversion

DDH1241 224.8 226.6 1.8 7.99 Ledbetter 04 Conversion

And 312.2 327.5 15.3 3.09 Ledbetter 04 Conversion

DDH1243 320.7 328.4 7.7 9.92 Ledbetter 04 Conversion

DDH1244 346.5 364.5 18.1 1.91 Ledbetter 04 Conversion

And 374.1 377.9 3.8 5.46 Ledbetter 04 Conversion

DDH1246 328.5 346.3 17.8 11.86 Ledbetter 04 Conversion

And 357.5 400.2 42.7 15.55 Ledbetter 04 Conversion

Including 360.5 363.6 3.1 145.25 Ledbetter 04 Conversion

Including 373.4 383.1 9.7 13.33 Ledbetter 04 Conversion

UGD0027 338.0 359.1 21.1 2.74 Horseshoe

Lower Conversion

UGD0029 300.3 340.8 40.5 13.30 Horseshoe

Lower Conversion

Including 300.3 310.0 9.7 46.79 Horseshoe

Lower Conversion

UGD0030 337.9 354.4 16.6 9.00 Horseshoe

Lower Conversion

And 399.6 408.0 8.4 5.06 Horseshoe

Lower Conversion

UGD0037 NSR Horseshoe

Extension Definition

UGD0046 182.3 196.0 13.7 3.42 Horseshoe

Extension

Definition

Hole ID From To

Interval Au Target Category

(m) (m) (m) (g/t)

UGD0048 NSR Horseshoe

Extension

Definition

UGD0049 NSR Horseshoe

Extension

Definition

UGD0050 403.3 427.5 24.2 2.47 Horseshoe

Extension

Definition

UGD0051 NSR Horseshoe

Extension

Definition

UGD0052 NSR Horseshoe

Extension

Definition

UGD0053 NSR Horseshoe

Extension

Definition

UGD0054 NSR Horseshoe

Extension

Definition

UGD0055 240.6 252.3 11.6 4.05 Horseshoe

Extension

Definition

UGD0056 236.0 263.3 27.2 1.45 Horseshoe

Extension

Definition

UGD0057 NSR Horseshoe

Extension

Definition

Note: Intervals are core length, not true width. “Conversion” intercept is within the current resource

model shell directed at converting Inferred to Indicated resource category, while “Definition” are

intercepts outside the current resource model shell directed at converting mineralization to an

Inferred resource category. NSR = No Significant Result.

For further information relating to drill hole data please refer to the Company's website

at https://investors.oceanagold.com/additional-drillhole-data.

For further information please contact:

Investor Relations:

Rebecca Henare, Director, Investor Relations

Tel: +1 (604) 678 4095

[email protected]

Media Relations:

Louise Burgess, Director, Communications

Tel: +1 (604) 403-2019

[email protected]

About OceanaGold

OceanaGold is a growing intermediate gold and copper producer committed to safely and responsibly

maximizing the generation of Free Cash Flow from our operations and delivering strong returns for our

shareholders. We have a portfolio of four operating mines: the Haile Gold Mine in the United States of

America; Didipio Mine in the Philippines; and the Macraes and Waihi operations in New Zealand.

Qualified Person Statement

The scientific and technical information contained in this press release has been reviewed and approved

by Craig Feebrey, a Member of the Australasian Institute of Mining and Metallurgy and a qualified person

under National Instrument 43-101 – Standards of Disclosure for Mineral Projects of the Canadian Securities

Administrators ("NI 43-101"). Mr. Feebrey is the Executive Vice President and Chief Exploration Officer of

OceanaGold.

QA/QC at Haile Gold Mine

From July 2017 to 2022 almost all Haile exploration core samples have been prepared at the ALS lab in

Tucson, Arizona, and analyzed at the ALS lab in Reno, Nevada, each of which is independent from

OceanaGold. Select resource conversion core samples were also prepared and analyzed at the SGS lab

in Kershaw, South Carolina, which is also independent from OceanaGold, with confirmation pulp duplicates

sent to ALS lab in Reno, Nevada. Samples are pulverized from a 250g (ALS) or 450g (SGS) sample to 85%

passing 75 mesh. Approximately 225g of pulp sample is used for fire assay. Assays are based on a 30g

fire assay aliquot for gold with Atomic Absorption finish. If the gold value from Atomic Absorption is >10g/t,

an additional 30g of pulp sample is fire assayed for gold using a gravimetric finish. Some holes are

composited and analyzed for carbon, sulphur and multi-elements using LECO and ICP-OES methods. Both

ALS and SGS labs used for Haile OceanaGold samples are ISO 17025 certified. In 2023, select resource

conversion core samples were prepared and analyzed at the SGS lab in Kershaw, South Carolina, with

confirmation pulp duplicates sent to ALS lab in Reno, Nevada.

Blanks and standards are each inserted every 20th sample.. Precision and accuracy of certified reference

materials (“CRMs”) compared to expected values have been consistently within 5% RSD and often within

3%. Barren marble and sand are inserted as blanks every 20th sample. CRMs from RockLabs are inserted

every 20th sample (5%). CRMs from RockLabs and OREAS are inserted every 20th sample (5%). All blanks

and CRMs are handled by the Geology Team and are stored in the locked OceanaGold office.

All drill hole samples are handled and transported from the drill rigs to the secured Haile Exploration

warehouse by OceanaGold personnel. Access to the property is controlled by locked doors and cameras

monitored by OceanaGold security. The main gate requires an electronic employee badge to enter.

Samples are packaged at the Haile Exploration warehouse by OceanaGold geologists and geotechnicians.

Samples are trucked in sealed plastic barrels by certified couriers with submittal forms that are verified

during sample pick -up and delivery to ALS. No sample shipments have been recorded as missing or

tampered with.

Technical Report

For further information, please refer to the following NI 43- 101 technical report available on the SEDAR+

website at www.sedarplus.com under the Company's profile or on our website at www.oceanagold.com:

"NI 43-101 Technical Report Haile Gold Mine Lancaster County, South Carolina" dated March 28, 2024

with an effective date of December 31, 2023, prepared by D. Carr, D, Londoño, J. Moore and B. Drury

(OceanaGold); L. Standridge and R. Cook (Call & Nicholas, Inc.); J.N. Janney -Moore and W.L. Kingston

(NewFields Mining & Technical Services LLC ); and M. Sullivan and B. Miller Clarkson (SRK Consulting

(U.S.), Inc.).