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
FORM 51-102F3
MATERIAL CHANGE REPORT
| ITEM 1. | Name and Address of Company |
Almaden Minerals Ltd. (“Almaden” or the “Company”)
210 - 1333 Johnson Street
Vancouver, British Columbia
V6H 3R9
| ITEM 2. | Date of Material Change |
May 19, 2026
A news release was issued and disseminated via GLOBE NEWSWIRE by
the Company on May 21, 2026.
| ITEM 4. | Summary of Material Change |
Almaden has continued with its international arbitration proceedings
(the “Claim”) against the United Mexican States (“Mexico”) under the Comprehensive and Progressive
Agreement for Trans-Pacific Partnership (“CPTPP”), by filing its Reply submission (“Reply”) with
the International Centre for Settlement of Investment Disputes (“ICSID”).
Almaden is pursuing this Claim together with Almadex Minerals Ltd.
(“Almadex”), on behalf of themselves and their Mexican subsidiaries (the “Claimants”). Prior to
the illegal acts of Mexico which resulted in the complete loss of the investment, Almaden held 100% of the Ixtaca precious metals project
in Mexico (the “Project”), while Almadex held a 2.0% NSR royalty on the Project.
The Reply builds upon and adds to the independent expert reports
and witness statements that formed part of the Memorial, and the Claimants are now seeking damages of US$2.68 billion, in the aggregate.
This number may be further updated as the Claim proceeds, to reflect future movements in precious metal prices, exchange rates, interest
rates, and other factors.
| ITEM 5. | Full Description of Material Change |
Almaden announced that it had filed its Reply relating to the Claim
against Mexico with ICSID.
The Claim is being prosecuted pursuant to the established and enforceable
legal framework of ICSID and is being funded through a US$9.5 million non-recourse litigation funding agreement provided by a leading
legal finance counterparty (see June 27, 2024 press release).
As further explained in the Company’s June 27, 2024 press
release, Almaden is pursuing this Claim together with Almadex, on behalf of themselves and their Mexican subsidiaries. Prior to the illegal
acts of Mexico which resulted in the complete loss of the investment, Almaden held 100% of the Ixtaca precious metals Project in Mexico,
while Almadex held a 2.0% NSR royalty on the Project.
The Reply comprehensively addresses the arguments presented in Mexico’s
Counter Memorial of December, 2025 and outlines Mexico’s breaches of the CPTPP through:
| · | the arbitrary denial on 17 December 2020 by Mexico’s environmental authority (“SEMARNAT”)
of Almaden’s environmental permit application for the Project; |
| · | the Mexican Supreme Court’s 16 February 2022 decision which ordered the suspension of the mineral
concessions underlying the Ixtaca deposit (the “Concessions”), a pronouncement on “feasibility”, and indigenous
consultations; |
| · | SEMARNAT’s bad faith campaign against the Project from at least December 2020 until February 2023;
and, |
| · | the determination issued by Mexico’s Mining Authority on 9 February 2023 which arbitrarily and retroactively
declared a lack of “feasibility” regarding the Concession titles that it had approved years earlier and validated several
times since, thereby cancelling the Concessions in full. |
The Reply builds upon and adds to the independent expert reports
and witness statements that formed part of the Memorial. Among the reports filed as part of the Reply is an independent quantum expert
report, updated to reflect movements in precious metal prices, interest rates, and other factors since the Claimant’s Memorial filing
in March, 2025. Based on this updated quantum estimate the Claimants now seek damages in the amount of US$2.68 billion, in the aggregate.
This number may be further updated as the Claim proceeds, to reflect future movements in precious metal prices, exchange rates, interest
rates, and other factors.
The next steps in the arbitration process include Mexico filing
its Rejoinder to the Claimants’ Reply, which is currently scheduled for late August, 2026 and then the in-person hearing in Washington
D.C, currently scheduled for December 14-18, 2026.
| ITEM 5.2. | Disclosure of Restructuring Transactions |
Not applicable.
| ITEM 6. | Reliance on Subsection 7.1(2) of National Instrument 51-102 |
Not applicable.
| ITEM 7. | Omitted Information |
There are no significant facts required to be disclosed herein
which have been omitted.
For further information, please contact:
Douglas McDonald, President & CEO
(604) 689-7644
info@almadenminerals.com
May 28, 2026
Safe Harbor Statement
Certain of the statements and information in this material
change report constitute “forward-looking statements” within the meaning of the United States Private Securities Litigation
Reform Act of 1995 and “forward-looking information” within the meaning of applicable Canadian provincial securities laws.
All statements, other than statements of historical fact, are forward-looking statements or information. Forward-looking statements or
information in this material change report relate to, among other things, the timing of any update regarding the arbitration calendar.
These forward-looking statements and information reflect
the Company’s current views with respect to future events and are necessarily based upon a number of assumptions that, while considered
reasonable by the Company, are inherently subject to significant legal, regulatory, business, operational and economic uncertainties and
contingencies, and such uncertainty generally increases with longer-term forecasts and outlook. These assumptions include: stability and
predictability in Mexico’s response to the arbitration process under the CPTPP; stability and predictability in the application
of the CPTPP and arbitral decisions thereon; the ability to continue to finance the arbitration process, and continued respect for the
rule of law in Mexico. The foregoing list of assumptions is not exhaustive.
The Company cautions the reader that forward-looking statements
and information involve known and unknown risks, uncertainties and other factors that may cause actual results and developments to differ
materially from those expressed or implied by such forward-looking statements or information contained in this material change report.
Such risks and other factors include, among others, risks related to: the application of the CPTPP and arbitral decisions thereon; continued
respect for the rule of law in Mexico; political risk in Mexico; crime and violence in Mexico; corruption in Mexico; uncertainty as to
the outcome of arbitration or the funding available to the Company to pursue it; as well as those factors discussed the section entitled
"Risk Factors" in Almaden's Annual Information Form and Almaden's latest Form 20-F on file with the United States Securities
and Exchange Commission in Washington, D.C. Although the Company has attempted to identify important factors that could affect the Company
and may cause actual actions, events or results to differ materially from those described in forward-looking statements or information,
there may be other factors that cause actions, events or results not to be as anticipated, estimated or intended. There can be no assurance
that our forward-looking statements or information will prove to be accurate. Accordingly, readers should not place undue reliance on
forward-looking statements or information. Except as required by law, the Company does not assume any obligation to release publicly any
revisions to on forward-looking statements or information contained in this material change report to reflect events or circumstances
after the date hereof or to reflect the occurrence of unanticipated events.
