Abbott H. Thayer (1849–1921), a prominent U.S. painter, was one of the first to describe in detail the function of protective coloration in nature. In military history, he frequently is credited with the first military applications of countershading and disruptive patterning, so that he was known among friends as ‘the father of camouflage’. This essay is a brief review of Thayer’s lifelong involvement in the study of both natural and military camouflage.