William Lidstone McKnight, DFC & Bar (18 November 1918 – 12 January 1941) was a Canadian aviator and flying ace of the Second World War. He was Canada's fifth-highest scoring ace of the war. McKnight joined the Royal Air Force (RAF) in early 1939 and served in No. 242 Squadron RAF during the final phase of the Battle of France, covering the Allied retreat from Brittany, and later the Battle of Britain.