John William Watson Stephens FRS (1865–1946) was a British parasitologist and expert on tropical diseases.

In World War I he was a malaria consultant with rank of Lieutenant-Colonel, Royal Army Medical Corps.

He was a member of the Colonial Medical Research Committee in 1927 and the president of the Royal Society of Tropical Medicine and Hygiene in 1927–1928.

One such species, namely Plasmodium ovale, was first described in 1914 by Stephens in a blood sample taken from a patient in Pachmarhi, Madhya Pradesh in the autumn of 1913.

In 1935 he conducted archaeological excavations on the nearby hill of Allt Cunedda, but made little record.