Roger Crab (1621 – 11 September 1680) was an English soldier, haberdasher, herbal doctor and writer who is best known for his ascetic lifestyle which included Christian vegetarianism. Crab fought in the Parliamentary Army in the English Civil War before becoming a haberdasher in Chesham. He later became a hermit and worked as a herbal doctor. He then joined the Philadelphians and began promoting asceticism through his writings.