Tony Cliff (born Yigael Gluckstein; 20 May 1917 – 9 April 2000), was a Trotskyist activist. Born to a Jewish family in Palestine, he moved to Britain in 1947 and by the end of the 1950s had assumed the pen name of Tony Cliff. A founding member of the Socialist Review Group, it eventually became the Socialist Workers Party in 1977 of which Cliff was effectively the leader.