Killen is a surname. Notable people with the surname include:
Louis Killen or Louisa Jo Killen (1934-2013), English Folk SingerChris Killen (born 1981), New Zealand professional footballerEdgar Ray Killen (born 1925), American criminalJames Killen (1925-2007), Australian politicianJohn Sidney Killen (1826-1903), American farmer and state legislatorWilliam Dool Killen (1806-1902), Irish Presbyterian minister and church historianWilliam M. Killen, (born 1938), American politicianWilliam Wilson Killen (1860–1939), Australian politician