Abstract: The invention provides a benzoxazine resin composition having excellent resistance to heat and moisture and providing excellent handleability when made into prepreg, and prepreg and a fiber-reinforced composite material prepared from the composition. The composition contains (A) a compound having in its molecule a benzoxazine ring represented by the formula (1), (B) an epoxy resin, (C) a curing agent, and (D) a toughness improver: (R1: C1 to C12 chain alkyl group, etc., and H is bonded to at least one of C of the aromatic ring at o- or p-position to the carbon atom to which the oxygen atom is bonded).