Abstract: A pet diaper extends in a lateral direction along a waist of a pet and in a longitudinal direction from a ventral side to a dorsal side of the pet, the lateral direction being orthogonal to the longitudinal direction, and the pet diaper includes: a main body including: an absorbent core; and a tail hole having a longitudinally elongated shape with a largest opening width in the longitudinal direction that is larger than a largest opening width in the lateral direction; a pair of fastening tabs, disposed closer to the ventral side than is the tail hole, that extend outward from a lateral side edge of the main body; and a target portion, disposed closer to the dorsal side than is the tail hole, that engages with the pair of fastening tabs.