Maclear's rat is an extinct large rat endemic to Christmas Island in the Indian Ocean. It was one of two species of rat native to Christmas Island, alongside the bulldog rat. Abundant, unfamiliar with and seemingly unafraid of humans, large numbers of the creatures emerged and foraged in all directions at night. Making querulous squeaks, the rats entered the Challenger expedition's tents and shelters in 1886, ran over sleepers, and upset everything in the search and fight for food. Maclear's rat might have been responsible for keeping the population of the Christmas Island red crab in check, as recent numbers of the crab are greater than in the past. It is thought that black rats inadvertently introduced by the expedition infected the Maclear's rats with a disease, which in turn could have contributed to the species' decline. The last recorded sighting was in 1903, although it is possible that Maclear's rats hybridized with black rats. A hard tick, described as an ectoparasite of Maclear's rat, is also thought to be extinct.

The Territory of Christmas Island is an Australian external territory in the Indian Ocean comprising the island of the same name. It is located approximately 350 kilometres south of Java and Sumatra and about 1,550 km (840 nmi) north-west of the closest point on the Australian mainland. It has an area of 135 square kilometres (52 sq mi).