The Mary B Mitchell was a British schooner which served as a Q-ship during the First World War. She was in service from April 1916 until the end of hostilities, operating in the Southwest Approaches from her base in Falmouth.She had several encounters with German U-boats in her career, and was credited with the destruction of two, though post-war analysis established that no U-boats were sunk. She had a reputation for being an efficient and successful vessel. After the war she returned to merchant service but was wrecked in 1944.