Timothy Richards Lewis (31 October 1841 – 7 May 1886) was a Welsh surgeon and pathologist who worked in India on several aspects of tropical medicine. He worked during the early period when the role of pathogenic organisms in disease were beginning to triumph over the older miasma theory. He was one of the first to identify the role of nematode worms in filariasis. His studies include those on cholera, leprosy, trypanosoma, and fungal infections. He is one of twenty three whose names are included in a frieze at the entrance of the London School of Hygiene and Tropical Medicine.