A forged piston for an internal combustion engine formed from an aluminum alloy containing silicon in an amount of 6 to 25 mass %, includes an oil ring groove section (12) and a skirt section (13). The ratio (A/B) of the average size (A) of eutectic silicon grains contained in the oil ring groove section to the average size (B) of eutectic silicon grains contained in the frontal end portion (18) of the skirt section is at least 1.5. The average size (A) is at least 4 μm. With the configuration such that the average size (B) is small and that the average size (A) is large, the skirt section exhibits excellent forgeability and the oil ring groove section exhibits reliable mechanical workability and improved wear resistance.