Mutual Aid: A Factor of Evolution is a 1902 collection of anthropological essays by Russian naturalist and anarchist philosopher Peter Kropotkin. The essays explore the role of mutually-beneficial cooperation and reciprocity (or "mutual aid") in the animal kingdom and human societies both past and present. It is an argument against theories of social Darwinism that emphasize competition and survival of the fittest, and against the romantic depictions by writers such as Jean-Jacques Rousseau, who thought that cooperation was motivated by universal love. Instead Kropotkin argues that mutual aid has pragmatic advantages for the survival of human and animal communities and, along with the conscience, has been promoted through natural selection.

Mutual Aid is considered a fundamental text in anarchist communism.