Len Siffleet (14 January 1916 – 24 October 1943) was an Australian commando of World War II.
Born in Gunnedah, New South Wales, he joined the Second Australian Imperial Force in 1941, and by 1943 had reached the rank of sergeant.
Posted to M Special Unit of the Services Reconnaissance Department, Siffleet was on a mission in Papua New Guinea when he and two Ambonese companions were captured by partisan tribesmen and handed over to the Japanese.
All three men were interrogated, tortured and later beheaded.
A photograph of Siffleet's impending execution became an enduring image of the war, and his identity was often confused with that of other servicemen who suffered a similar fate, in particular Flight Lieutenant Bill Newton.