Canarium decumanum is a tree in the family Burseraceae. The specific epithet ' is from the Latin meaning 'greatest', referring to the size of the tree and the fruit.
Canarium decumanum grows up to tall with a trunk diameter of up to . The grey bark is smooth to scaly. The flowers are yellow-brown. The fruits are ellipsoid and measure up to long.
Canarium decumanum grows naturally in Borneo, the Moluccas and New Guinea. Its habitat is lowland forests.