Sir William Henry Cowan (22 May 1862 – 11 January 1932) was a politician in the United Kingdom. The son of William Cowan and Elizabeth Giles, he was educated at Merchiston Castle School, Edinburgh Collegiate School and the University of Edinburgh. As of 1928, he was chairman of Parkinson and W. and B. Cowan, Limited, a manufacturer of gas meters and gas cookers. He was knighted in the 1917 Birthday Honours.