Macrotarsomys petteri, also known as Petter's big-footed mouse, is a Malagasy rodent in the genus Macrotarsomys. With a head and body length of 150 mm (5.9 in) and body mass of 105 g (3.7 oz), Macrotarsomys petteri is the largest species of its genus. The upperparts are brown, darkest in the middle of the back, and the underparts are white to yellowish. The animal has long whiskers, short forelimbs, and long hindfeet. The tail ends in a prominent tuft of long, light hairs. The skull is robust and the molars are low-crowned and cuspidate.