The Old Left is a term used to describe Western Leninists, both Stalinist and Trotskyite, to differentiate them from the non-Leninist Marxists of the New Left who emerged between the 1950s and the 1970s.

The Old Left tended to emphasise the importance of party organisation and class consciousness over the cultural agenda of the New Left influenced by Antonio Gramsci and the Frankfurt School.

Some people claim that the American neoconservative movement has its origins in the Old Left, many of whose disenchanted members moved to the political right following disillusionment with the policies of the Soviet Union.