OceanaGold : 2023 Sustainability Report

OceanaGold

Health and Safety

Personal Safety

Behavioural Safety and

Workplace Engagement

Occupational Health and Hygiene

Community

Community Engagement Sustainable Development

Human Rights

Human Rights Due Diligence

Indigenous Peoples

Modern Slavery and

Responsible Sourcing

People and Culture

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OceanaGold

2023 Key Sustainability Performance Outcomes

Governance & Strategy

Independently assured OceanaGold's conformance with the Responsible Gold Mining Principles and Conflict-Free Gold Standard

Completion of the Global Industry

Standard on Tailings

Management gap assessment

Launched the Supplier Code

of Conduct

Board approval of the Company's

Sustainability Strategy and updated Climate Change Strategy

Achieved Morgan Stanley Capital

International (MSCI) "AA" and MSCI "Leader" rating

Health and Safety

Total Recordable Injury Frequency Rate (TRIFR) per million hours worked of 4.4, up from 2.3 in 2022

Category 4 (and above) Injury Severity Rate of 0.22, down from 0.48 in 2022

OurSafe Behaviours program launched

Stop and Think program refreshed

Human Rights

Human Rights Impact

Assessments completed

at all operations

100% of OceanaGold Executives

have completed human rights training

Social Performance

Social investment contributions of over

$9M

Over $198M spent with local suppliers

Environment

Zero material environmental events

Significant progress on Reefton

Restoration Project, an industry-leadingpost-mining rehabilitation project approaching return to the New Zealand Department of Conservation

Climate Change

Energy and greenhouse-gas emission- reduction plans developed for all sites

Energy and emission reduction

projects incorporated into Life of Mine plans and budgets

People

New culture survey launched, with above-benchmark engagement scores

Collective bargaining negotiations completed with no industrial

downtime

Values-based recognition program launched with over 200 nominations

New supervisor program launched to support culture and performance aspirations

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OceanaGold

We are pleased to share with you OceanaGold's 2023 Sustainability Report.

"Throughout OceanaGold we seek to embed sustainability in our daily practices, with a

At OceanaGold our approach to sustainability is driven by our Purpose, which is to mine gold for a better future. This focus on the value we strive to create for our stakeholders - our people, the communities that host us, our business partners, and shareholders - informs our strategic and day- to-daydecision-making. It is reflected in our Vision to be a company people trust, want to work and partner with, supply and invest in, to create value. Our approach to sustainability is also brought to life by our shared Values of Care, Respect, Integrity, Performance, and Teamwork.

Throughout OceanaGold we seek to embed sustainability in our daily practices, with a particular focus on keeping our people safe and healthy, reducing our environmental impacts, and creating benefits and opportunities beyond our mines.

Delivering value through responsible business practices

Our commitment to operating safely and responsibly stretches from the Board to front line operations. In 2023, 25% of OceanaGold's 2023 objectives in the Company-wide annual incentive program were related to health, safety, energy- use and decarbonization, environmental and social performance, and our culture. This has been increased to 29% in 2024 to further reflect the importance we place on delivering our results in a responsible way.

During the year we strengthened the sustainability capability of our Board with the appointment of Linda Broughton in April 2023. Linda has significant experience in environmental geochemistry, water and tailings management, and mine reclamation and closure. In addition, the Board undertook training on climate change and new mandatory climate change reporting in December 2023. The Board will undertake refreshed human rights and diversity, equity, and inclusion training in 2024.

The Board also approved two important strategies in 2023 - the updated Sustainability Strategy and updated Climate Change Strategy - reflecting our awareness of evolving stakeholder expectations and the ongoing focus required to meet our stated aspirations across the sustainability spectrum, including in relation to operational emissions.

We also updated our Sustainability Committee Charterto ensure it appropriately reflects the Company's priorities. Focus areas of the Board in 2023 included safety, occupational hygiene, environmental compliance, tailings management and improvements to our Risk Management Framework.

particular focus on keeping our people safe and healthy, reducing our environmental impacts, and creating benefits and opportunities beyond our mines."

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OceanaGold

2023 year in review

2023 was another solid year of delivering value for our shareholders. Record average realized gold prices and strong annual production of 477,313 ounces of gold - in-line with our Guidance

• allowed us to achieve our highest-ever revenues, be free cash flow positive and increase returns to shareholders through the re-introduction of a semi- annual dividend.

We ended the year in a solid financial position.

Our liquidity, overall financial strength and projected performance positions us to continue to operate the business in a safe and responsible manner, progress the organic growth opportunities in our portfolio and increase returns to shareholders.

Keeping our people safe

The health, safety and wellbeing of our people remains of paramount importance. Our unwavering goal is that everyone working at OceanaGold returns home safely every day.

Though our Total Recordable Injury Frequency Rate (TRIFR) per million hours worked increased from 2.3 in 2022 to 4.4 in 2023, our overall injury severity was lower in 2023. During the year, we launched the OurSafe Behaviours program to personalise, encourage and empower everyone to work safely. The program identifies peer-selected safety leaders across operational sites to help embed specific safe behaviours in their respective work environments. We also refreshed our Stop and Think program, to ensure safety is front of mind prior to undertaking tasks.

During the year we increased our focus on understanding and managing occupational health and hygiene. All sites completed occupational

We remain committed and energized to keep the safety and health of our workforce as an area of unrelenting focus in 2024.

Building a winning culture

Our people and culture are integral to our success. To be a company where people want to work requires our people to feel valued, respected and empowered to contribute their skills, abilities and perspectives. This starts with having a culture that reflects our Values, not just on paper but in how we interact every day. To recognize our people who exemplify our Values in their work we launched a Living Our Values recognition program in 2023. We are proud of our first cohort of winners of this award, who are inspiring their colleagues through their actions.

In 2023, we also invested in developing frontline leadership capability in order to better equip our leaders with the skills required to lead, which in turn will benefit the teams they lead. This program will continue and be expanded upon in 2024.

To further align, incentivize and recognize the contributions of our people to our business performance, we expanded our Long-Term Incentive Program to include all salaried employees. We believe this is a powerful and effective way to have our people working together to achieve our common goals.

Finally, our efforts to build a winning culture are bearing fruit. In our 2023 Culture Survey, 75% of our employees reported feeling engaged, which is higher than the industry benchmark average and 76% of employees reported an intent to stay with the Company for over three years. 74% of our workforce participated in the survey, which is 40-50% more than in 2022.

We are a significant employer in the communities where we operate and we aim to use local suppliers where commercially practical to maximize the economic development of the communities near our mines. In 2023, we spent almost $200 million on procuring goods and services from local suppliers.

We contributed over $9 million to social investment projects in communities around our operations.

At Didipio, this included a scholarship program for local Indigenous People and the ongoing building of local roads to facilitate the movement of farm produce to markets. At Waihi, we continued our annual donation to the Waihi Gold Mining Education Trust to help fund local students' university studies.

Managing our environmental impacts

Ensuring we are managing our impacts today for the world we want tomorrow is at the forefront of our business decisions. We are proud to report we had no significant environmental incidents in 2023 and all sites continued to maintain and implement their biodiversity management plans.

We established and implemented Energy and Carbon Reduction Plans at each site to deliver key initiatives helping reduce our emissions intensity by 30% by 2030. These include initiatives to commence decarbonizing mobile equipment and electricity supply and to improve energy efficiency.

We commissioned an external gap assessment of our Tailings Storage Facilities (TSFs) against the Global Industry Standard for Tailings Management requirements, which subsequently informed the development of a 2-year alignment plan that we aim to implement throughout 2024 and 2025. All of our sites have conducted Comprehensive Dam Safety Reviews on their TSFs.

Strengthening human rights and supplier governance

Operating with integrity is a value of the Company and an expectation of all our stakeholders. In 2023, we progressed Human Rights Impact Assessments at all our operations. All our Executives completed human rights training and we continued to conduct focused training across our workforce. We also developed and released a Supplier Code of Conduct, which provides high-level guidance on responsible business practices we expect our suppliers to adhere to.

Looking ahead: delivering on organic growth safely and responsibly

As we look ahead, we will continue to explore opportunities that will unlock further value across OceanaGold. Responsible business practices are integral to this as it is only through listening to our stakeholders, minimizing our impacts and delivering on our promises that we can continue to be a preferred and trusted partner. Our business objectives are achieved not only by what we do but also how we do it.

2024 is set to be an exciting year for us as we deliver organic production growth and, subject to operating and market conditions, strong free cash flow. We plan to deliver on our Vision to a company that people want to work and partner with, supply and invest in, to create value.

Gerard Bond

President and Chief Executive Officer

exposure monitoring baselines which will help us develop and evaluate better long-term controls throughout 2024 and beyond.

Investing in communities

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OceanaGold

Message from our Chief Sustainability Officer

During my first 12 months with OceanaGold, I have had the pleasure of meeting our many talented teams and have built a strong understanding of the business and our sustainability practices, risks and opportunities. In this time, I have seen firsthand the strong sustainability platform we have in place and the personal commitment our people demonstrate to operating safely and responsibly.

Across our business I have consistently observed strong integrity in action, a caring culture,

an unwavering commitment to building and maintaining trusting and respectful relationships with stakeholders - particularly with our host communities, iwi in New Zealand, and our regulators everywhere - and a genuine desire to continuously learn and improve in everything we do. Coupled with our commitment to the Responsible Gold Mining Principles and the United Nations Global Compact, which are foundational to how we operate, we have a strong platform on which to build.

Standing still is not an option however, as we know that to keep pace with evolving stakeholder needs and expectations, we must closely monitor and adapt to our changing external environment.

With this in mind, we developed two key strategies in 2023 - an updated Sustainability Strategy and an updated Climate Change Strategy. Both take a 3-year view and consider material issues for our stakeholders as well as new and emerging requirements, issues and trends. These have been approved by our Board of Directors.

Our Sustainability Strategy reflects OceanaGold's commitment to safe and responsible mining and a business-wide focus on continuous improvement. It is based on four strategic focus areas, each of which will be supported by annual performance metrics from 2025:

1. Health and Safety;
2. External Affairs and Social Performance;
3. Environment (including water, biodiversity and circularity); and
4. Decarbonization and Climate.

The Sustainability Strategy aims to build on our strong foundations to be excellent in sustainability relative to our intermediate gold mining peers. We intend to deliver on our commitments consistently and will systematically consolidate, strengthen and embed the things that really matter. By doing so, we aim to further enhance the trust we have with our stakeholders and build an even more resilient business.

"Across our business I have consistently observed strong integrity in action, a caring culture, an unwavering commitment to building and maintaining trusting and respectful relationships with stakeholders and a genuine desire to continuously learn and improve in everything we do."

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OceanaGold

Our updated Climate Strategy reflects our pursuit of reducing our carbon emissions per ounce of gold produced by 30% by 2030. In 2024, we will develop a Climate Transition Plan that will strive to be robust, practical, commercially sound and achievable. In addition to demonstrating how we will achieve our goals, we are doing this to ensure the business is able to meet the heightened climate change disclosure requirements while progressing decarbonization efforts at sites.

These two updated strategies are timely. 2023 represented a step change in global corporate sustainability reporting with the International Sustainability Standards Board (ISSB) launching its new Sustainability Disclosure Standards - IFRS S1 and IFRS S2 - under the International Financial Reporting Standards (IFRS) umbrella. These were developed to provide globally comparable sustainability-related disclosures for investors.

Concurrently, leading mining industry bodies - the World Gold Council, The Copper Mark, the Mining Association of Canada, and the International Council on Mining and Metals - also announced a commitment to consolidate their voluntary best practice responsible mining standards into a single responsible mining standard, and multi-stakeholder oversight system. This new standard is expected to be launched in 2024.

These global developments have brought enhanced alignment around responsible business expectations, disclosures, measurement, and accountability, particularly regarding climate change. For companies like OceanaGold, who operate across multiple jurisdictions, these changes remove some of the complexity and enable us

to demonstrate our strengths. Simultaneously however, we are confronted with an increased reporting burden as different jurisdictions create their own mandatory playbook on the new standards, and we are faced with navigating multiple timelines and boundary definitions.

For us to meet these requirements effectively and efficiently, we will continue to evolve our approach to address mandatory reporting requirements, while also evaluating which frameworks and standards make the most sense for us and which resonate most clearly with our stakeholders.

OceanaGold's commitment to safe and responsible mining is foundational to our Purpose of mining gold for a better future. We will continue to strive to do what we say we will, well, everyday, to create value for our stakeholders.

Megan Saussey

Chief Sustainability Officer

"OceanaGold's commitment to safe and responsible mining is foundational to our Purpose of mining gold for a better future."

OceanaGold 2023 Sustainability Report

Megan and our Process Manager onsite at our Didipio Mine.

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Overview

About This Report

This 2023 Sustainability Report ("Report" or "Disclosure") is OceanaGold Corporation's annual Company disclosure of sustainability performance.

This Sustainability Report has been prepared with reference to theGlobal Reporting Initiative (GRI) Standards and the GRI G4 Mining and Metals Sector Disclosures and is reviewed by the responsible operational and Company representatives, relevant Management, and the Executive Leadership Team. It has been approved by the OceanaGold Board Sustainability Committee.

We have adopted the same boundary and approach as we have in previous years. This Disclosure incorporates all operating assets, development projects and exploration projects during the 2023 reporting period (1 January to 31 December 2023).

Our operating assets comprise:

• Haile Gold Mine, South Carolina, United States of America (USA);
• Didipio Mine, Luzon Island, Philippines;
• Waihi Operation, North Island, New Zealand; and
• Macraes Operation, South Island, New Zealand.

Our exploration activity in 2023 was focused on tenements on or near the above-mentioned mining operations. The Report also includes some information about our corporate offices and sites undergoing closure or relinquishment.

This Report should be read in conjunction with OceanaGold's year-on-yearInteractive Environment, Social and Governance (ESG) Data and the Basis of Preparation.

Unless otherwise stated, all financial figures in this report have been converted to US dollars (USD) using a weighted average provided in the table below.

References to "OceanaGold", "the Company", "we" and "our" refer to OceanaGold Corporation and our subsidiaries unless explicitly stated otherwise.

TABLE 1 - 2023 Weighted average exchange rates

Bureau Veritas Australia (BV) provided independent limited assurance for select 2023 sustainability reporting disclosure data and statements, in conformance with International Standard on Assurance Engagements (ISAE) 3000 (see Appendix 2). BV has also undertaken assurance assessments on:

• OceanaGold Corporation's2023 Responsible Gold Mining Principles Implementation and Conformance Report
• OceanaGold Corporation's2023Conflict-FreeGold Statement

We welcome feedback on this Sustainability Report or any aspect of our sustainability performance via sustainability@oceanagold.com.

Other reports and information available on ourwebsite include our:

• Responsible Mining Framework, governance policies, statements of position, standards and guidelines;
• Modern Slavery Statement;
• Annual Information Form;
• Quarterly Financial Reports and Management's Discussion and Analysis;
• Extractive Sector Transparency Measures Act (ESTMA) Report;
• Annual General Meeting Circular, corporate presentations, news and insights; and
• Information on our operating assets, development projects, offices and exploration.