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.

[1] While making studies of chyluria, he noticed worms in the urine of a patient which was later found to be filaria and were independently discovered and described by Joseph Bancroft.

[2][3][4] Lewis examined microscopic organisms in the blood of birds and mammals,[5] and named several species of microbes including a trypanosome, Trypanosoma lewisi, from a rat.

Cuningham), several of whom opposed the contagion theory which would lead the implementation of quarantine regulations that would come greatly in the way of trade and movement.