John Henry Clarke (1853 – 24 November 1931) was a prominent English classical homoeopath. He was also, arguably, the most important anti-Semite in Great Britain. He led The Britons, an anti-Semitic organisation. Educated at the University of Edinburgh, he received his medical degree in 1877. Clarke was a busy practitioner. As a physician, he not only had his own clinic in Piccadilly, London, but he also was a consultant at the London Homeopathic Hospital and researched into new remedies — nosodes.