OceanaGold Corporation (TSX: OGC) (OTCQX: OCANF) announces results from 6 drill holes from the ongoing exploration and resource conversion program at Wharekirauponga, located approximately 10 kilometres to the north of the Company’s Waihi operation in New Zealand.

Wharekirauponga Drilling Highlights (estimated true width):

• 14.9 m @ 16.3 g/t Au from 466.5 m, EG Vein (WKP144B)
• 5.4 m @ 25.8 g/t Au from 483.4 m, EG Vein (WKP144A)
• 5.5 m @ 24.1 g/t Au from 623.6 m, EG Vein (WKP124N)
• 6.4 m @ 19.1 g/t Au from 470.7 m, EG Vein (WKP144C)
• 5.4 m @ 6.6 g/t Au from 443.5 m, EG HW Veins (WKP144B)
• 2.5 m @ 10.3 g/t Au from 436.9 m, EG HW Veins (WKP144B)

Gerard Bond, President and CEO of OceanaGold, said “Today’s drill results from Wharekirauponga continue to demonstrate the upside of this exceptional orebody. Drilling indicates a newly emerging high-grade zone that sits outside of reserves, at the southern extent of the known deposit. Importantly, the newly defined high-grade zone is located closer to the planned underground access. With Wharekirauponga remaining open in multiple directions, we remain well positioned to drive shareholder value through continued resource growth and conversion as we increase the amount of drilling this year.”

Drill results can be viewed in 3D using VRIFY at the following link:

https://vrify.com/meetings/recordings/852c6a5b-6fe4-488f-b10f-0ca92c8aae87

Wharekirauponga Drill Results Overview

Since the Company’s November 25, 2025 news release, a total of 6 drill holes have been completed and results returned from the EG, hanging wall (“HW”) and footwall (“FW”) Veins, collectively referred to as the “EG Vein zone” (Figure 1). Notably, drill results in the southern portion of the EG Vein continue to define the emergence of a new high-grade zone that is on the periphery of the Inferred Mineral Resource but sits outside the Mineral Reserves.

East Graben (“EG”) Vein

Drilling from site 9 returned multiple wide, high-grade intercepts demonstrating the continuity of the system in the southern area. Results included 14.9 m @ 16.3 g/t Au (WKP144B) and 5.4 m @ 25.8 g/t Au (WKP144A) (Figure 2). These results support increased confidence in the resource model and extend high-grade mineralization up-dip on the southern portion of the resource. The newly defined southern high-grade zone, encompassing seven drill holes (including previously reported holes) averaging above 160 gram metres, currently spans 150 metres in strike. This area remains open in multiple directions and is a target for follow-up drilling later this year.

At drill site 8, conversion drilling results were above expectations, including 5.5 m @ 24.1 g/t Au (WKP124N). While previous interpretations suggested that the upper extent of the EG Vein was geometrically constrained, new results suggest that the mineralization is dipping more shallowly than previously interpreted and there remains the potential for further up-dip extensions of the EG Vein (Figure 3). Follow-up drilling is also planned for this area.

Hanging Wall and Footwall Veins

The HW and FW Veins and associated extensional sub-parallel structures that lie immediately to the east and west, respectively, of the EG Vein also yielded strong results. WKP144-series (A,B,C) holes returned high-grade mineralization including 5.4 m @ 6.6 g/t Au (WKP144B) and 2.5 m @ 10.3 g/t Au (WKP144B) (Figure 4). These results highlight a zone of high‑grade mineralization outside of the current resource model that are largely unconstrained due to limited drilling, yet lies in immediate proximity to the EG Vein and represents a target for future drilling.

Wharekirauponga 2026 Exploration Program

Three drill rigs are operating at drill sites 1, 8, and 9 at Wharekirauponga (Figure 1). We expect to add an additional two drill rigs during the second quarter of 2026 on new drill platforms in accordance with the permit approval in December 2025. Drilling for 2026 will continue to focus on improving resource confidence and further resource growth.

Table 1: Wharekirauponga drill intersections subsequent to the press release dated November 25, 2025, results update

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

https://oceanagold.com/operations/additional-drillhole-data.

About OceanaGold

OceanaGold is a global 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 wholly-owned Haile Gold Mine in the United States of America; the wholly-owned Macraes and Waihi operations in New Zealand; and the 80%-owned Didipio Mine in the Philippines.

Qualified Person Statement

The scientific and technical information in this press release has been reviewed and approved by Mr. Leroy Crawford-Flett, a Chartered Professional 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 Mr. Crawford-Flett is the Exploration & Geology Manager of the Waihi Operation.

Quality Assurance and Quality Control

All exploration samples are assayed for gold by 30g fire assay with AAS finish. Since mid-2022, drill core sample intervals where visible electrum is logged are followed up by a subsequent screen fire assay after the routine 30g fire assay. Core samples were prepared and analyzed at the independent SGS Waihi NZ Ltd laboratory (Au by 30g fire assay and Ag by aqua regia digest and 0.3gm AAS finish. Samples post April 2024 with Ag, As, Sb. Hg and S by ICP-MS after DIG12R Digest). Selected pulps are periodically sent to the independent ALS laboratory 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 independent 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; and
• Monitoring of accuracy of the primary SGS assay and ALS results through insertion Certified Reference Materials (“CRMs”) 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 QA/QC protocol at Waihi requires CRMs to be reported to within 2 standard deviations of the certified value, for preparation duplicates to have a relative difference (R-R1/mean RR1) of no greater than 10%, and for blanks to not exceed more than 5 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 a monthly basis by OceanaGold geologists. No sampling risks have been recorded during these visits.