Walter Medley Tattersall (8 November 1882 – 5 October 1943) was a British zoologist and marine biologist, famous for his study of mysids. He was born in Liverpool, the eldest son of a draper's family. He studied zoology at the University of Liverpool, where he graduated in 1901. Subsequently, he worked as a naturalist for the Irish Fisheries Department under Ernest William Lyons Holt, where he began his studies of crustaceans. In 1909 he became the director of the Manchester Museum and also worked as a tutor in marine biology at the universities of Manchester and Sheffield.