Mastixia trichotoma is a tree in the family Nyssaceae. The specific epithet ' is from the Greek meaning 'three parts', referring to the three-branched inflorescence.
Mastixia trichotoma grows as a tree measuring up to tall with a trunk diameter of up to . The smooth to fissured bark is yellowish grey to grey-brown. The flowers are green to yellowish green. The to ellipsoid fruits measure up to long.
Mastixia trichotoma grows naturally in the Andaman and Nicobar Islands, Thailand, Sumatra, Peninsular Malaysia, Java, Borneo, Sulawesi, the Moluccas and Mindanao. Its habitat is mixed dipterocarp forests from sea-level to elevation.