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.^[1] 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.^[1] 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.^[1]

During World War I, he served as a private in Flanders and France, where he was wounded and gassed in 1918. In the middle of the war, in 1916, he married Olive Selden Attride (1890–1978).^[1]

In 1922, he was appointed professor at the University of Cardiff, a post he would hold for the rest of his life.^[1] He was highly respected as a teacher in zoology and marine biology and also as a field researcher and taxonomist. Tattersall has an impressive publication record; he is the taxonomic authority for a large number of crustaceans, in particular of mysids and euphausiids. Most of the illustrations in his publications were drawn by his wife Olive who was a notable carcinologist in her own right.

• Tattersall, W. M. & O. S. Tattersall (August 2003). British Mysidacea. Pisces Conservation Ltd. ISBN 1-904690-09-2.