Walter William Ouless (1848–1933) was a British portrait painter from Jersey. He became an Associate of the Royal Academy (ARA) in 1877 and a full member (RA) in 1881.
He was born in 1848 at 53 Paradise Row, New Street, Saint Helier, at the home where his father, marine artist Philip John Ouless, had established his studio in the previous year. His mother was Caroline Savage. He was educated at Victoria College and went to London in 1864, where he entered the Royal Academy schools in 1865. His earliest work was in the field of genre painting, but his compatriot Millais advised him to concentrate on portrait painting, in which field he established a successful career. In later life he turned to landscape painting.
Ouless was "one of the best-known portraitists of the latter years of the nineteenth century", regarded as an "impressive exponent of character".
He was a volunteer in the Artists Rifles. His daughter Catherine Ouless (1879–1961) also achieved success as an artist.