Tony Cliff (born Yigael Glückstein, Hebrew: יגאל גליקשטיין; 20 May 1917 – 9 April 2000) was a Trotskyist activist.

Born to a Jewish family in Ottoman Palestine, he moved to Britain in 1947 and by the end of the 1950s had assumed the pen name of Tony Cliff.

He was one of four children born to Akiva and Esther Glückstein, Jewish immigrants from Poland, who had come to Palestine as part of the Second Aliyah.

He had two prominent uncles: the noted doctor Hillel Yaffe and agronomist and Zionist activist Haim Margaliot-Kalvarisky [fr].

In his youth, he came to identify with Communism, though he never joined the Palestine Communist Party, as he had not met any of its members before becoming a socialist activist.

[1] In prison, he met Meir Slonim, general secretary of the Palestine Communist Party, Avraham Stern and Moshe Dayan.

This debate was linked to other discussions on the nationalised industries in Britain and the increasingly critical stance of Haston and the RCP as to the leadership of the Fourth International with regard to Eastern Europe and Yugoslavia in particular.

[citation needed] By the time he gained permanent residency in Britain his supporters in The Club had been expelled due to differences on Birmingham Trades Council regarding socialist policy concerning the Korean War, where Glückstein's co-factionalists refused to take a position of support for either side in the war.

[7] Cliff was a revolutionary socialist in the Trotskyist tradition, attempting to make Lenin's theory of the party effective in the present day.

However, Cliff himself was insistent that his ideas owed nothing to those of Max Shachtman, or earlier proponents of the theory such as Bruno Rizzi, and made this clear in his work Bureaucratic Collectivism – A Critique.

[8] Cliff had little or no time for any activities not directly linked to the needs of building his party (with the exception of caring for his family).

As well as authoring many articles on social questions for the group's publications, she was an activist in the National Union of Teachers until her retirement.