Cezary Ketling-Szemley (22 July 1915 – 9 January 1979) was a Polish military officer and lawyer. He was a participant in the Polish resistance movement during the World War II, member of the PLAN, Home Army and PAL, main collaborator and supporter of the Jewish Military Union (ŻZW) on the part of the Polish underground during and before the Warsaw Ghetto Uprising. He was born as Cezary Szemley. During the war he used the aliases "Janusz", "Ketling", "Olgierd" and "Arpad". After the war, he signed himself Cezary Szemley-Ketling or Ketling-Szemley. In 1949, he officially changed his name to Janu