John O'Brien (1831 – 1891) was a Canadian marine artist.
O'Brien is believed to have been born at sea as his Irish family emigrated from County Cork. He emerged as a self-taught artist in Halifax, Nova Scotia in the 1850s. O'Brien excelled at ship portraits and dramatic storm scenes. His career flourished as Nova Scotia's shipping industry grew and among his many notable paintings include a portrait of the famous clipper Stag and dramatic storm portraits of the warship HMS Galatea. O'Brien studied with English landscape artist John W. Carmichael from 1857 to 1858. At the height of his career in 1859, he suffered a partial loss of vision. His career suffered in the 1870s, when he produced very few works, but revived in the 1880s.