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OceanaGold Continues to Delineate High-Grade Gold Mineralization at Haile and Wharekirauponga

Drill Results

December 14, 2023

News Release

OceanaGold Continues to Delineate High-Grade Gold Mineralization at

Haile and Wharekirauponga

(VANCOUVER) OceanaGold Corporation (TSX : OGC) (“OceanaGold” or the “Company”) is pleased to

provide an update on results from the 2023 exploration and resource conversion programs at Haile in the

United States and Wharekirauponga in New Zealand.

Gerard Bond, President & CEO of OceanaGold, said “ 2023 has been a succes sful year for resource

conversion at OceanaGold. Drill re sults released during this year highlight the upside potential for growth

within our existing mine footprint at Haile, while results at Wharekirauponga continue to demonstrate the

exceptional grade and continuity within the EG vein. Today’s drill results provide increased confidence in

our resource base and will be reflected in our updated reserves and resource statement to be released

early next year.”

Highlights

• Haile resource conversion highlights include (core length):

• 73.8m @ 16.17g/t Au, Horseshoe (UGD0008 - conversion)

• 19.1m @ 8.63g/t Au and 31.4m @ 9.59g/t Au, Horseshoe (UGD0017 - conversion)

• 22.6m @ 5.43g/t Au, Horseshoe (UGD0003 - conversion)

• 73.2m @ 4.92g/t Au, Palomino (DDH1194 - conversion)

• 21.3m @ 6.15g/t Au, Palomino (DDH1197 - conversion)

• Wharekirauponga resource conversion highlights include (estimated true width intersections):

• 5.0m @ 77.1g/t Au and 111.6g/t Ag, EG Vein (WKP118B – conversion)

• 8.4m @ 42.2g/t Au and 90.7g/t Ag, EG Vein (WKP118A – conversion)

• 4.4m @ 41.6g/t Au and 54.2g/t Ag, EG HWS Vein (WKP118B – conversion)

• 3.7m @ 39.1g/t Au and 70.3g/t Ag, EG HWS Vein (WKP118A – conversion)

• 1.5m @ 79.2g/t Au and 208.2g/t Ag, EG Vein (WKP121 – conversion)

• 3.8m @ 25.8g/t Au and 106.0g/t Ag, EG Vein (WKP111B – conversion)

Haile

A program of resource conversion drilling at Horseshoe Underground totalling ~18,400 metres (“m”) is

scheduled to be completed by the end of 2024. To date, conversion drilling totalling 6,513m in fifteen holes

has been completed, with 3,896m completed since the September 14, 2023 news release. Drilling from

underground has targeted the conversion of the lower Horseshoe I nferred resource with 12 holes to date

and assay results from four new holes since the last update. Highlights from recent drilling include 73.8m

@ 16.17g/t Au from hole UGD0008, in line with the block model estimate, and is similar to hole UGD0002

returning 73.9m @ 13.03g/t Au released in September 2023.

Results were received from five remaining resource conversion holes at Palomino , located approximately

800m southwest of the Horseshoe Underground mine, where future access may be gained from

underground infrastructure. Highlights included 73.2m @ 4.92g/t Au (incl uding 9.1m @ 9.63g/t Au) in hole

DDH1194 and 21. 3m @ 6.15g/t Au (including 4.6m @ 16.32g/t Au) in hole DDH1197. The Palomino

resource conversion drill program is now complete, all assay results have been received, and modelling is

underway for a resource update in early 2024.

Figure 1: Long section (looking north-west) showing Palomino and Horseshoe with new drillhole

results annotated

Note: Significant intercepts are classified as grade >1.5g/t Au and length >3m with g/t x thickness

>12g/t*m

Wharekirauponga

Since the June 19, 2023 e xploration update, 5,700m have been drilled at Wharekirauponga, targeting the

conversion of Inferred resources in the EG Vein Zone (Figure 2). New intercepts for the EG vein and the

EG Hanging Wall Splay (“EG HWS”) continue to increase confidence in the geologic model and high-grade

continuity of the deposit. Opportunities remain for up-plunge, down-plunge and along-strike extensions of

the EG Vein. High-grade intercepts remain open. Step-out drilling in hole WKP100, the most southerly hole

on the EG Vein (previously released), confirmed mineralisation continues for at least a further 200 m along

strike of the currently defined southern shoot. A new drill site is being consented to enable drill testing of

the south-westerly strike extensions of the mineralisation above hole WKP100. The EG Vein Zone remains

the primary, near -term target for drilling with resource conversion and extensional drilling to continue

through the remainder of 2023 and 2024.

Figure 2: Wharekirauponga plan view of geology, drill traces and distribution of vein zones

Figure 3: Long section of the EG vein drill intersections (new holes labelled)

Figure 4: Long section of the EG HWS vein highlighting (new holes labelled)

Table 1: Haile drill intersections. NSR = No Significant Result. Intervals are core length, not true width. Conversion drilling

is within the current resource model shell.

Hole ID From (m) To (m) Interval (m) Au (g/t) Target Category

DDH1190 468.6 477.4 8.8 1.66 Palomino Conversion

and 493.0 506.7 13.7 1.99 Palomino Conversion

and 517.4 529.6 13.7 1.59 Palomino Conversion

and 540.2 552.4 12.2 5.79 Palomino Conversion

including 546.3 548.8 2.5 18.68 Palomino Conversion

including 563.1 581.4 18.3 2.64 Palomino Conversion

DDH1194 377.1 450.2 73.2 4.92 Palomino Conversion

including 390.9 399.9 9.1 9.63 Palomino Conversion

DDW1195 531.1 544.8 13.7 4.71 Palomino Conversion

and 552.4 564.6 12.2 2.24 Palomino Conversion

and 581.9 587.5 5.6 2.78 Palomino Conversion

DDH1197 463.0 484.3 21.3 6.15 Palomino Conversion

including 475.2 479.7 4.6 16.32 Palomino Conversion

DDW1202 381.6 412.9 31.2 3.58 Palomino Conversion

and 435.0 448.7 13.7 2.54 Palomino Conversion

UGD0003 309.2 331.8 22.6 5.43 Horseshoe Conversion

UGD0005 NSR Horseshoe Conversion

UGD0008 306.0 379.8 73.8 16.17 Horseshoe Conversion

including 313.3 347.1 33.8 28.53 Horseshoe Conversion

UGD0017 302.6 321.7 19.1 8.63 Horseshoe Conversion

and 349.4 380.8 31.4 9.59 Horseshoe Conversion

including 349.4 356.6 7.2 18.07 Horseshoe Conversion

Table 2: Wharekirauponga drill intersections. Intervals are estimated true width. Conversion drilling is within the current

resource model shell.

Hole ID From (m) To (m) True Width (m) Au (g/t) Ag (g/t) Target Category

WKP111A 485.9 486.5 0.6 17.0 13.0 EG HWS Conversion

and 487.9 491.8 3.6 14.8 13.8 EG Conversion

WKP111B 494.3 498.7 3.8 25.8 106.0 EG Conversion

WKP111C 504.8 508.8 3.5 19.5 13.8 EG Conversion

WKP111E 536.2 539.2 2.1 13.3 9.9 EG Conversion

WKP118A 455.1 457.5 2.0 36.0 39.4 EG HWS Conversion

and 459.4 463.9 3.7 39.1 70.3 EG HWS Conversion

and 498.8 509.0 8.4 42.2 90.7 EG Conversion

and 539.2 542.2 1.6 11.2 14.5 EG FW Conversion

WKP118B 465.1 470.5 4.4 41.6 54.2 EG HWS Conversion

and 509.7 516.8 5.0 77.1 111.6 EG Conversion

WKP120 286.6 288.9 2.0 10.1 17.3 EG Conversion

and 354.7 356.3 1.1 17.2 40.4 EG FW Conversion

WKP121 271.8 273.5 1.5 79.2 208.2 EG Conversion

WKP122 306.6 308.3 1.4 14.0 33.8 EG Conversion

WKP123 307.3 310.4 2.0 8.9 27.2 EG Conversion

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

at https://oceanagold.com/investor-centre/tsx-asx-filings.

For further information please contact:

Investor Relations:

Rebecca Harris, Director, Investor Relations

Tel: +1 604 678 4095

[email protected]

www.oceanagold.com

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 exploration results in this press release were prepared in accordance with National Instrument 43-101

– Standards of Disclosure for Mineral Projects of the Canadian Securities Administrators ("NI 43- 101").

Information relating to the Haile and Wharekirauponga exploration results in this document ha ve been

verified and are based on and fairly represent information compiled by or prepared under the supervision

of Craig Feebrey, a Member of the Australasian Institute of Mining and Metallurgy and an employee of

OceanaGold. Mr Feebrey has sufficient experience that is relevant to the style of mineralisation and type

of deposit under consideration and to the activity being undertaken to qualify as Qualified Persons for the

purposes of the NI 43-101. Mr Feebrey consents to the inclusion in this public report of the matters based

on their information in the form and context in which it appears.

QA/QC at Haile Gold Mine

Since July 2017 all Haile exploration core samples have been prepared at the ALS lab in Tucson, Arizona,

and analysed at the ALS lab in Reno, NV. Samples are pulverized from a 450g 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 3g/t Au. Some holes are composited and analysed for carbon,

sulphur and multi -elements using LECO and ICP -OES methods. ALS labs used for Haile OceanaGold

samples are ISO 17025 certified.

Blanks and standards are inserted every 20th sample. Check assays are submitted to the SGS lab in

Kershaw, SC for 5% of the intervals each quarter. Assays are duplicated for >95% of the samples within

5% of their original assay. ALS samples show no evidence of contamination or instrument drift. Precision

and accuracy of CRMs compared to expected values have been consistently with 5% RSD and often within

3%. Graphs showing expected values and two standards of deviation have been produced and evaluated.

Barren marble and sand are inserted as blanks every 20th sample. Certified reference mat erials from

RockLabs are inserted every 20t h sample. All blanks and CRMs are handled by the Geotech Supervisor

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 the Geotech Supervisor 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 Reports

For further information, please refer to the following NI 43-101 technical report:

a) “NI 43-101 Technical Report Haile Gold Mine Lancaster County, South Carolina” dated March 31,

2022, prepared by D. Carr, Chief Metallurgist, G. Hollett, Group Mining Engineer, and J. Moore,

Chief Geologist, each of OceanaGold Management Pty Limited, Michael Kirby of Haile Gold Mine,

Inc., J. Poeck, M. Sullivan, D. Bird, B. S. Prosser and J. Tinucci of SRK Consulting, J. Newton

Janney-Moore and W. Kingston of Newfields and L. Standridge of Call and Nicholas.

The above document has been filed with the Canadian securities regulatory authorities and is available for

review electronically from the Canadian System for Electronic Document Analysis and Retrieval (SEDAR)

at www.sedar.com under the Company’s profile.

QA/QC at Wharekirauponga, Waihi Gold Mine

All exploration samples are assayed for gold by 30 g fire assay with AAS finish. Since mid-2022 drill core

sample intervals where visible electru m is logged are followed up by a subsequent screen fire assay after

the routine 30g fire assay. Holes WKP40- 45 had core samples shipped for sample preparation to SGS in

Westport (New Zealand). Prepared pulps were then shipped to independent Australian Laboratory Services

Pty Ltd (ALS) in Brisbane, accredited to ISO/NATA 17025 for gold analysis by fire assay and 4-acid digest,

and 42 element ICP geochemical analysis. Holes drilled after WKP45 (i.e., WKP46 to WKP118) were

prepared and analysed at SGS Waihi NZ Ltd (Au by 30g fire assay and Ag by aqua regia digest and 0.3gm

AAS finish). Selected pulps are periodically sent to ALS in Brisbane for a 4- acid digestion and 42 or 48

element ICP geochemical analysis.

Quality of exploration assay results has been monitored in the following areas:

• Sample preparation at the SGS Waihi and Westport labs through sieving of jaw crush and pulp

products.

• Monitoring of assay precision through routine generation of duplicate samples from a second split

of the jaw crush and calculation of the fundamental error.

• Monitoring of accuracy of the primary SGS assay and ALS results through insertion of Certified

Reference Materials (CRM’s) and blanks into sample batches.

Blank, duplicate and CRM results are reviewed prior to uploading results in the AcQuire database and again

on a weekly basis. The protocol at Waihi requires CRMs to be reported to within 2 standard deviations of

the certified value. The criterion for preparation duplicates is that they have a relative difference (R-R1/mean

RR1) of no greater than 10%. Blanks should not exceed more than 4 times the lower detection value of the

assay method. Failure in any of these thresholds triggers an investigation and if appropriate re-assay. Drill

core is stored within secure facilities on site to which access is controlled. Site employees transport samples

to the analytical laboratory which is also a secured facility. The SGS Waihi NZ Ltd laboratory is an

independent commercial geochemistry and energy assay laboratory with ISO 17025: 2017 accreditation,

audited by an external consultant in 2020, and is inspected on an annual basis by OceanaGold geologists. No

sampling risks have been recorded during these visits.

Technical Reports

For further information, please refer to the following NI 43-101 technical report and the Company’s new s

release titled “OceanaGold Reports Growing High- Grade Resources at WKP in New Zealand” dated

February 24, 2020:

(a) “Waihi District Study - Preliminary Economic Assessment NI 43-101 Technical Report” dated August

30, 2020 , prepared by T. Maton, Study Manager and P. Church, Principal Resource Development

Geologist, both of Oceana Gold (New Zealand) Limited, and D. Carr, Chief Metallurgist, of OceanaGold

Management Pty Limited.

Both of the above documents have been filed with the Canadian securities regulator y authorities and are

available for review electronically from the Canadian System for Electronic Document Analysis and

Retrieval (SEDAR) at www.sedar.com under the Company’s profile.