Named after the British explorer John Whitehead who first documented its existence, Whitehead's spiny rat (Maxomys whiteheadi) has reddish-brown upperparts with grey underfur. As its name suggests, Whitehead's spiny rat also has numerous inflexible grey spines with black tips on its upperparts, which are thought to be for protection. The underparts are orange-buff with grey underfur and numerous soft, pale spines.

The tail, which is shorter than the head and body length combined, is bicoloured, with a brown-black upperside separated from a white underside by a sharp line.

Male Whitehead's spiny rats generally have longer hindfeet than females. This species of rat has the largest teeth of all Maxomys species. Six subspecies of Whitehead’s spiny rat are currently recognized, all of which differ slightly in appearance.