First Phosphate Reports Updated Mineral Resource Estimate for

First Phosphate Corp (CSE: PHOS) (OTCQX: FRSPF) (OTCQX ADR: FPHOY) (FSE: KD0) (“First Phosphate” or the “Company”) is pleased to announce the results of its updated Mineral Resource Estimate (“MRE”) for its Bégin-Lamarche project in Saguenay-Lac-Saint-Jean, Québec, Canada. The updated MRE includes results from the 2025-2026 drilling program described in the Company’s press release dated April 27, 2026.

• The updated MRE includes a 378% increase in Indicated Mineral Resources over the Company’s Initial MRE dated September 9, 2024.

• Measured pit-constrained Mineral Resource: 6.2 Mt @ 7.70% P2O5 (phosphate).

• Indicated pit-constrained Mineral Resource: 198.5 Mt @ 6.00% P2O5.

• Inferred pit-constrained Mineral Resource: 89.5 Mt @ 6.16% P2O5.

• The Deposit remains open at depth.

• Metallurgical test work indicates an anticipated apatite concentrate grade of 40.4% P2O5 at an 88% process recovery rate, with very low levels of potentially deleterious elements, and has been qualified for production of battery-grade phosphoric acid for lithium iron phosphate (“LFP”) battery with a conversion ratio of 91.1%.

• The Deposit is located next to existing road and hydroelectric infrastructure and at only 70 km driving distance from the deep-sea Port of Saguenay.

• The Deposit benefits from definitive, long-term, partially prepaid offtake from an existing, creditworthy partner.

• Apatite (phosphorus, phosphate) is listed on the critical minerals lists of Québec, Canada, the United States and the European Union.

“We are pleased with the results of our 2025-2026 drilling exploration program and the quantity and quality upgrade provided to our Mineral Resources,” says First Phosphate CEO, John Passalacqua. “We are now able to continue to move the project forward with great confidence in our Mineral Resources.”

The updated MRE, with an effective date of May 1, 2026, was carried out by Mr. Antoine Yassa, P.Geo., of P&E Mining Consultants Inc., who is an Independent Qualified Person within the meaning of Canadian Securities Administrators’ National Instrument 43-101: Standards of Disclosure for Mineral Projects (“NI 43-101”).

The Bégin-Lamarche Phosphate Deposit contains a significant phosphate Mineral Resource that is associated with well-defined oxide-apatite peridotite (OAP) intrusions within the large Lac-Saint-Jean anorthosite suite (LSJAS). The LSJAS is the largest phosphate-mineralized anorthosite worldwide. The phosphate Deposit is comprised of four mineralized zones which are continuous, only separated by faults within the Deposit and extend over a length of 2,750 m (Figure 1). The Mountain Zone is a single phosphate-bearing mass having a diameter of up to 200 m and a length of 250 m. The Northern zone is comprised of four phosphate layers ranging from 30 m to 200 m in thickness and a length of 625 m. The Central Zone bears eight phosphate layers, one of them having up to 50 m in thickness and extending to 900 m. The Southern Zone bears three phosphate layers, one of them having…