Alamos Gold announced that it has announced that it has announced that the company's Base Case Life of Mine Plan Outlining One of the Largest and Lowest-Cost Gold Mines in Canada with Significant upside potential through a further expansion of the operation, and the expected conversion of a significant portion of the large Mineral Resource base to Mineral Reserves through ongoing delineation drilling. Low-cost structure: average mine-site all-in sustaining costs ("mine-site AISC") of $915 per ounce over the initial 12 years (2026+), a 19% decrease from the mid-point of 2025 guidance. Average total cash costs of $581 per ounce over the initial 12 year (average $699 per ounce over the life of mine).

Average AISC of $1,003 per ounce over the life of Mine, an 11% decrease from 2025 guidance Long-life operation supported by a large and growing Mineral Reserve base. 48% increase in total Mineral Reserves to 6.3 million ounces (88.6 million tonnes ("mt") grading 2.23 grams per tonne ("g/t Au"), including: 4.1 million ounces grading 10.85 g/t Au (11.8 mt) at Island Gold underground, up 80% from the end of 2024 reflecting the conversion of Mineral Resources. 2.2 million ounces grading 0.91 g/t Au (76.9 mt) at Magino open pit, up 12% from the end of 2024.

Significant upside potential expected to be outlined in an Expansion Study in the fourth quarter of 2025. Base Case LOM Plan based only on Mineral Reserves and long-term milling rates of 12,400 tonnes per day ("tpd"). Expansion Study expected to include an increase in milling rates potentially to between 18,000 and 20,000 tpd supporting higher throughput rates from both Island Gold and Magino, and The incorporation of a larger Mineral Reserve through the expected conversion of a significant portions of existing Mineral Resources, which consist of: Island Gold Underground.

M&I Mineral Resources: 1.0M oz grading 10.49 g/t Au (3.1 mt); Inferred Mineral Resources: 1.3M oz grading 16.88 g/t Au (2.4 mt); Magino Open Pit; M&I Mineral Resources:1M oz grading 0.91 g/T Au (60.3 mt); Inferred Mineral Resources; 1.2M oz grading 0.92 g/t Au (40.3 mt); Low capital intensity; Growth capital of $453 million with the majority to be spent over the next two years, focused on completing the Phase 3+ Expansion and Magino mill expansion to 12,400 tpd; Sustaining capital of $1,808 million over the life of mine, or $304 per ounce; Sustaining capital intensity expected to decrease within Expansion Study reflecting a larger Mineral Reserve leveraging existing infrastructure; Total all-in cost of $1,079 per ounce, including total capital intensity of $380 per ounce.