William Lambe FRCP (26 February 1765 – 11 June 1847) was an English physician and early veganism activist.

He was educated at Hereford Grammar School,[2] where he was head boy, and St John's College, Cambridge, graduating B.D.

Moving to London about 1800, Lambe was admitted a Fellow of the College of Physicians in 1804, becoming a censor (examiner) and delivering the Croonian Lecture on several occasions between 1806 and 1828 and the Harveian Oration in 1818.

Lambe was considered an eccentric by his contemporaries, mainly on the ground that he was a strict, but not fanatical, vegetarian and that his favourite prescription was filtered water.

Lambe suffered from a variety of chronic diseases so gave up animal food in 1806 and embraced a vegetable and distilled water diet.

[6] Lambe believed that a distilled water and vegetarian diet could cure almost every known disease, including cancer.

In The Ethics of Diet, 1833 Howard Williams concluded that "Dr. Lambe occupies an eminent position in the medical literature of vegetarianism, and he divides with his predecessor, Dr. Cheyne, the honour of being the founder of scientific dietetics in this country.