Washington, D.C. 20549
Indicate by check mark whether the registrant files or will file annual
reports under cover of Form 20-F or Form 40-F.
Pursuant to the requirements of the Securities Exchange Act of 1934,
the registrant has duly caused this report to be signed on its behalf by the undersigned, thereunto duly authorized.
Exhibit 99.1

NEWS RELEASE
Fortuna publishes its 2025 Sustainability Report
Vancouver, May 28, 2026: Fortuna Mining Corp.
(NYSE: FSM | TSX: FVI) is pleased to announce the publication of its eighth annual Sustainability Report, highlighting 2025 progress
across governance, corporate strategy, risk management, and operational performance.
The report outlines Fortuna’s continued
focus on the sustainability priorities most material to its business and stakeholders, reflecting a year of portfolio consolidation, strengthened
systems, and operational discipline.
Jorge A. Ganoza, President, and CEO, stated, “2025
was a year of meaningful progress for Fortuna, as we strengthened our operational and sustainability performance while advancing key strategic
growth priorities. At the same time, we faced a tragic reminder that our commitment to Zero Harm must remain unwavering. Sustainability
is embedded in every aspect of our business, guiding decision-making and reinforcing our long-term commitment to our people, our communities,
and responsible mining.”
Julien Baudrand, Senior Vice President of Sustainability,
commented, “In 2025, we focused on reinforcing the systems, controls, and behaviors to ensure sustainability performance is consistently
delivered across our operations. We made tangible progress in critical risk management, water and tailings governance, and climate change
action. These efforts strengthen our ability to manage current and future risks proactively while supporting the development of new projects.”
Strategic highlights
During 2025, Fortuna continued to strengthen its
sustainability management culture through the implementation of several key initiatives, including:
| · | Reinforcing Fortuna’s Health and Safety
approach through the Critical Risk Management program, active field leadership initiatives and practical training programs. |
| · | Advancing our renewable energy projects helping
reduce energy costs in the context of rising fuel prices and our GHG emissions, including the solar plants at the Lindero and Séguéla
mines. Progressing on tailings management practices in alignment with the Global Industry Standard on Tailings Management (GISTM). |
| · | Integrating the Diamba Sud Gold Project into
Fortuna’s sustainability framework and advancing programs to ensure a high level of readiness before construction. |

Key facts and figures from the 2025 Sustainability
Report:
Governance
| · | 63% of directors have expertise in safety, sustainability,
and ESG |
| · | 37.5% of Board members are women |
| · | 30% of executive short-term incentive compensation
is tied to sustainability performance |
Workforce Health and Safety
| · | One fatal incident involving a subcontractor |
| · | Lost Time Injury Frequency Rate (LTIFR): 0.00 |
| · | Total Recordable Injury Frequency Rate (TRIFR):
0.74 |
| · | 100% of operating mines certified under ISO 45001
|
Labor Relations, Human Rights, and Business
Ethics
| · | Zero confirmed cases of human rights violations
or corruption |
| · | 4,286 total workers (employees and contractors) |
| · | 18% female representation in management positions |
Community Relations
| · | Zero significant community disputes or non-technical
delays |
| · | US$258 million in contributions to governments |
| · | US$4.36 million invested in community programs |
| · | 33% of employees from local communities |
Environment
| · | Zero significant environmental spills |
| · | Zero water-related regulatory non-compliance
incidents |
| · | 100% of operating mines certified under ISO 14001 |
| · | Carbon intensity: 0.41 tCO₂e per gold equivalent
ounce |
| · | 17% of energy consumption from renewable sources |
| · | Water consumption intensity: 0.19 m³ per
tonne |
| · | 65% water recycled or reused |

Looking ahead to 2026
In 2026, Fortuna’s sustainability priorities
remain focused on strengthening operational discipline, risk management, and long-term resilience across the business. Key priorities
include:
| · | Continuing to improve effectiveness and consistency
of Critical Risk Management, with particular emphasis on field verification activities and contractor Health and Safety performance. |
| · | Advancing water and tailings governance while
continuing the integration of physical climate risk considerations into mining operations and development projects. |
| · | Consolidating sustainability systems across the
portfolio, including readiness initiatives at Diamba Sud, to ensure social and environmental considerations are embedded from the earliest
stages of development. |
| · | Reinforcing the behaviors, systems, and capabilities
that support the Company’s social license to operate, particularly in areas where water stewardship, land use, and community expectations
intersect. |
The 2025 Sustainability
Report also highlights success stories and sustainability performance across Fortuna’s mines and projects in Latin America and West
Africa, reflecting
the broader impact of the Company’s activities. The report demonstrates how strong operational performance can advance meaningful
social and environmental outcomes, strengthen local communities, and support shared sustainability priorities.
As part of its commitment
to transparency, Fortuna prepares its disclosures using internationally recognized standards and guidance frameworks, including SASB,
IFRS S1, GRI, and TCFD, while continuing to advance toward alignment with IFRS S2. The Company also provides expanded sustainability data
through its Sustainability Data Book and Interactive Analyst Center, offering
detailed site-level and corporate performance information.
Fortuna’s 2025 Sustainability Report
is available on our website at www.fortunamining.com
Questions and feedback are welcomed at: sustainability@fmcmail.com

About Fortuna Mining Corp.
Fortuna Mining
Corp. is a Canadian precious metals mining company with three operating mines and exploration activities in Argentina, Côte d’Ivoire,
Guinea, Guyana, and Peru, as well as the Diamba Sud Gold Project located in Senegal. Sustainability is integral to all our operations
and relationships. We produce gold and silver and generate shared value over the long-term for our stakeholders through efficient production,
environmental protection, and social responsibility. For more information, please visit our website at www.fortunamining.com
ON BEHALF OF THE BOARD
Jorge A. Ganoza
President, CEO, and Director
Fortuna Mining Corp.
Investor Relations:
Carlos Baca | info@fmcmail.com |
fortunamining.com | X | LinkedIn | YouTube | Instagram | TikTok
Forward-Looking Statements
This news release contains forward-looking
statements which constitute “forward-looking information” within the meaning of applicable Canadian securities legislation
and “forward-looking statements” within the meaning of the “safe harbor” provisions of the Private Securities
Litigation Reform Act of 1995 (collectively, “forward-looking statements”). All statements included herein, other than statements
of historical fact, are forward-looking statements, including, without limitation, statements pertaining to the Company’s sustainability
plans, targets, strategies, and goals, such as working towards a zero harm workplace, implementing the Global Industry Standard for Tailings
Management, and minimizing our environmental footprint. Often, but not always, these forward-looking statements can be identified by the
use of words such as “believe”, “expect”, “anticipate”, “contemplate”, “target”,
“plan”, “goal”, “budget”, “aim”, “intent”, “estimate”, “may”,
“should”, “could”, “future” and similar expressions, including negative variations.
Forward-looking statements involve known and
unknown risks, uncertainties and other factors which may cause the actual results, performance, or achievements of the Company to be materially
different from any results, performance or achievements expressed or implied by the forward-looking statements. Such risks, uncertainties,
and factors include, among others, risks associated with climate change; risks associated with mining regime changes in the Company’s
operating jurisdictions, including those related to permitting and approvals, environmental and tailings management, labour, trade relations,
and transportation, other factors including accidents, equipment breakdown, environmental risks; as well as those factors discussed under
“Description of the Business - Risk Factors” in the Company’s Annual Information Form, a copy of which can be found
on the Company’s profile on the SEDAR+ website at www.sedarplus.ca. Although the Company has attempted
to identify important factors that could cause actual actions, events, or results to differ materially from those described in forward-looking
statements, there may be other factors that cause actions, events, or results to differ from those anticipated, estimated or intended.
Forward-looking statements contained herein are based on the assumptions, beliefs, expectations, and opinions of management, including,
but not limited to, continued availability of water and power resources at the Company’s operations; financial and physical impacts
of climate change and climate change initiatives on markets and the Company’s operations; the availability and effectiveness of
technologies needed to achieve the Company’s sustainability goals and strategies; the accuracy of the Company’s current mineral
resource and reserve estimates; that the Company’s activities will be in accordance with the Company’s public statements and
stated goals; and that there will be no material adverse change affecting the Company or its properties. Forward-looking statements are
made as of the date hereof and the Company disclaims any obligation to update any forward-looking statements, whether as a result of new
information, future events or results or otherwise, except as required by law. There can be no assurance that forward-looking statements
will prove to be accurate, as actual results and future events could differ materially from those anticipated in such statements. Accordingly,
investors should not place undue reliance on forward-looking statements.