Sir William Henry Allchin (1846–1912) was an English physician and lecturer on comparative anatomy, physiology, pathology and medicine.

[2] Born in Paris, William Allchin was the eldest son of a physician from Bayswater and entered University College, London to study medicine.

He served as chief surgeon of the SS Great Eastern for 5 years when the ship was laying cable.

[2] On 19 August 1880, Allchin married Margaret, daughter of Alexander Holland of New York.

[3] This English biographical article related to medicine is a stub.