Symplocos costatifructa is a tree in the family Symplocaceae, native to Borneo. The specific epithet costatifructa means 'ribbed fruit'.
Symplocos costatifructa grows up to 10m (30feet) tall, with a trunk diameter of up to . The brown bark is smooth. The leathery leaves measure up to long, occasionally to . The inflorescences feature white flowers. The egg-shaped fruits are white, ribbed and measure up to long.
Symplocos costatifructa is endemic to Borneo, where it is known from Sabah, Sarawak and Brunei. Its habitat is kerangas and mixed dipterocarp forests, at elevations of .