We describe three new species of Fulvifomes from Thailand, all of which grow on Xylocarpus granatum, a major mangrove tree species in southeastern Asia. Fulvifomes xylocarpicola sp. nov. is characterized by the perennial and sessile basidiocarps, woody context without a distinct crust, pores 4–6/mm, a dimitic hyphal system both in the context and trama, broadly ellipsoid basidiospores measuring 4–5.5 × 3.5–4.5 μm, and occurrence on the stem of X. granatum. Fulvifomes siamensis sp. nov. is characterized by the perennial and sessile basidiocarps, woody context without a crust, pores 7–8/mm, a monomitic hyphal system in the context, subglobose basidiospores measuring 4.5–6 × 4–5 μm, and occurrence on the root or butt of X. granatum. Fulvifomes halophilus sp. nov. is characterized by perennial, sessile basidiocarps, leathery to corky context with a crust near the pileus surface, pores 5–8/mm, a subdimitic hyphal system in the context, subglobose basidiospores measuring 4–5.5 × 3.5–5 μm, and occurrence on the root or butt of X. granatum. Fulvifomes mangrovicus comb. nov. is proposed for Fomes mangrovicus. A key to the worldwide species of Fulvifomes is provided.