Mr. Jorge Ganoza reports

FORTUNA FILES ENVIRONMENTAL AND SOCIAL IMPACT ASSESSMENT FOR THE DIAMBA SUD GOLD PROJECT IN SENEGAL AND PROVIDES UPDATE ON PRELIMINARY ECONOMIC ASSESSMENT STATUS

Fortuna Mining Corp. has filed an environmental and social impact assessment (ESIA) for the Diamba Sud gold project with the Direction de la Reglementation Environnementale et du Controle (DiREC), which is part of the Ministry of the Environment and Sustainable Development of Senegal. The filing of the ESIA marks an important milestone in the permitting process and reinforces the company's commitment to advancing Diamba Sud to a construction decision in the first half of 2026. Fortuna also provides an update on the status of the project's preliminary economic assessment (PEA) and continuing drilling activities.

Jorge A. Ganoza, president and chief executive officer, commented: "The filing of the ESIA represents a key step forward in advancing Diamba Sud towards development. The document contains Fortuna's commitment to high environmental and social standards and to working in partnership with government, host communities and various stakeholders in Senegal." Mr. Ganoza continued, "We plan to complete the project's preliminary economic assessment during the fourth quarter and move to a definitive feasibility study and construction decision during the first half of 2026."

Highlights:

• Submission of ESIA to the Senegalese authorities in accordance with national legislation and alignment with international standards;
• ESIA covers the project description and benefits for the country, the institutional and regulatory framework, environmental and social baseline studies, the public consultation, impact assessment, and proposed mitigation and monitoring plans and programs;
• PEA (preliminary economic assessment) study advancing on schedule, with completion planned during the fourth quarter of 2025;
• 52,110 metres drilled year to date in 2025, leading to a mineral resource expansion for the project of 53 per cent in the measured and indicated category and 93 per cent in the inferred category for the project (refer Fortuna's news release dated Aug. 5, 2025);
• Drilling is planned to restart during October after the end of the rainy season and will continue until year-end with the aim of testing extensions of open mineralization.

Environmental and social impact assessment

The submission of the ESIA is a prerequisite for obtaining an environmental permit, which forms part of the overall permitting process required for project development. The ESIA addresses key environmental and social considerations associated with the potential development of Diamba Sud, including:

• Compliance with all applicable national regulations and alignment with the Equator Principles and IFC (International Finance Corp.) Performance Standards;
• Regular engagement with local communities and national stakeholders to integrate feedback into project design and planning;
• Environmental and social management plans designed to mitigate impacts and enhance local benefits, such as environmental and social management plan, stakeholder engagement plan, capacity building plan, livelihood restoration program, mine rehabilitation and closure plan, and a voluntary environmental and social investment program.

Preliminary economic assessment status

Fortuna is advancing work on the PEA for Diamba Sud, which will provide a first look at the project's potential economics and development alternatives. Engineering, metallurgical test work and trade-off studies are currently under way, with completion scheduled for early in the fourth quarter of 2025. A definitive feasibility study (DFS) will follow the PEA in the first half of 2026, incorporating results from the ESIA process, and drilling is to be completed by year-end.

Drilling program update

Fortuna has advanced its 2025 drilling program with a total of 52,110 metres completed to date. Exploration continues to focus on resource expansion, infill drilling, and testing of new targets defined by recent geochemical and geophysical surveys.

Recent highlights include the delineation of a maiden inferred mineral resource at Southern Arc of 3.85 million tonnes at an average gold grade of 1.57 grams per tonne containing 194,000 ounces of gold (refer Fortuna's news release dated Aug. 5, 2025), where mineralization remains open at depth and along strike to the east and south. Drilling to test the Southern Arc extensions is scheduled to resume in early October with four drill rigs after the conclusion of the annual rainy season.

Drilling will also continue to advance project generation and target testing across Diamba Sud and the contiguous Bondala exploration property, where several geochemical, structural and geophysical anomalies have been identified.

Qualified person

Eric Chapman, senior vice-president, technical services, is a professional geoscientist of the Association of Professional Engineers and Geoscientists of British Columbia (registration No. 36328) and a qualified person as defined by National Instrument 43-101, Standards of Disclosure for Mineral Projects. Mr. Chapman has reviewed and approved the scientific and technical information contained in this news release and has verified the underlying data.

About Fortuna Mining Corp.

Fortuna Mining is a Canadian precious metals mining company with three operating mines and a portfolio of exploration projects in Argentina, Ivory Coast, Mexico and Peru as well as the Diamba Sud gold project in Senegal. Sustainability is at the core of the company's operations and stakeholder relationships. Fortuna Mining produces gold and silver while creating long-term shared value through efficient production, environmental stewardship and social responsibility.

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