Oswald Wykeham Cornwallis OBE (16 March 1894 – 28 January 1974) was an English Royal Navy officer and amateur cricketer. He was born in 1894 at Linton Park in Kent, the third son of Mabel and Fiennes Cornwallis. His father was the Member of Parliament for Maidstone and would later become a peer. He served in both the First and Second World Wars.
Cornwallis served in the Navy in both world wars, rising to the rank of Captain. He played first-class cricket for the Navy between 1920 and 1926.
Cornwallis was educated at Royal Naval College, Osborne and Royal Naval College, Dartmouth before being commissioned in the Royal Navy as a Midshipman in 1911. He served during the First World War, rising to the rank of Lieutenant during the war, and was awarded an OBE in 1919 as a result of his war service on HMS Caroline in the 4th Light Cruiser Squadron. After the war he was promoted to Lieutenant commander and then, in 1928, to Commander and took command of HMS Scarborough between 1933 and 1935.
At the beginning of the Second World War Cornwallis was serving in the Admiralty in Southampton as Liaison Officer for the Royal Naval Reserve and Merchant Navy. During the war he served as the deputy director of Naval Equipment, stationed at HMS President in London. He retired from the navy with the rank of Captain in 1944.