OceanaGold Corporation announced 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). Drill results can be viewed in 3D using VRIFY at the following link: https://vrify.com/meetings/recordings/852c6a5b-6fe4-488f-b10f-0ca92c8aae87.

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". 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. 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). 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.

Follow-up drilling is also planned for this area. 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).

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. Three drill rigs are operating at drill sites 1, 8, and 9 at Wharekirauponga. They 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 Drill Hole ID From To True width Au Ag Vein Activity (m) (m) (m) (g/t) (g/t) WKP124O 582.5 587.3 2.0 20.9 11.5 EG Vein Conversion WKP124N 623.6 636.5 5.5 24.1 29.9 EG Vein Conversion WKP144A 483.4 491.1 5.4 25.8 18.0 EG Vein Conversion WKP144B 466.5 483.7 14.9 16.3 12.2 EG Vein Conversion WKP144C 470.7 478.1 6.4 19.1 13.4 EG Vein Conversion WKP144 373.1 376.3 2.9 5.9 7.0 EGHW Veins Definition WKP144A 459 461 1.3 10.4 7.6 EGHW Veins Definition WKP144B 407.3 409.8 2.1 11.6 6.9 EGHW Veins Definition WKP144B 436.9 439.8 2.5 10.3 7.3 EGHW Veins Definition WKP144B 443.5 450.5 5.4 6.6 5.4 EGHW Veins Definition WKP144C 433.6 434.7 1.0 20.5 17.0 EGHW Veins Definition. Notes: "Definition" drilling intercepts are intercepts outside the current Resource model shell directed at defining mineralization to an Inferred Mineral Resource category and "Conversion" drilling are intercepts converting Inferred Mineral Resources to Indicated Mineral Resources category.

NSR = No Significant Result. For further information relating to drill hole data please refer to the Company's website at https://oceanagold.com/operations/additional-drillhole-data. 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 ("NI 43-101").