William Killen may refer to:
William Dool Killen (1806–1902), Irish Presbyterian minister and church historian William Wilson Killen (1860–1939), Australian politician Bill Killen (William M. Killen, born 1938), American politician William Killen (1722–1805), Irish-born first chief justice and first chancellor under the Constitution of 1792 of the state of Delaware, U.S.