The term ultra-leftism has two overlapping uses. One usage is a generally pejorative term for certain types of positions on the far left that are seen as extreme or intransigent. The term is also used—pejoratively or not—to refer to a particular current of Marxist communism, which is closely related to council communism and left communism.
Ultra-left currents within left communism are often subject to criticisms from other factions of the left. The left communist organization International Communist Current refuses to work with leftist groups except other left communists or anarchists. Gilles Dauvé (also known as Jean Barrot), a left communist theorist, argues that all bourgeois regimes should be opposed, and that revolutionaries should not defend liberal democracy against fascism.
The term ultra left is rarely used in English, in which people tend to speak broadly of left communism as a minor variant of traditional Marxism. The French equivalent, ultra-gauche, has a stronger currency, as it is a more positive term in that language and is used to define a movement that still exists today: a branch of left communism descending from theorists such as Amadeo Bordiga, Otto Rühle, Anton Pannekoek, Herman Gorter and Paul Mattick, and continuing with more recent writers, such as Jacques Camatte and Gilles Dauvé.
Far-left politics or extreme-left politics are politics further on the left of the left-right spectrum than the mainstream political left.
Dr. Luke March of the School of Social and Political Science at the University of Edinburgh, defines the "far left" in Europe as those that place themselves to the left of social democracy, which they see as insufficiently left-wing. The two main sub-types are the so-called "radical left", for their desire for fundamental change to the capitalist system while accepting of democracy, and the "extreme left" who are more hostile to liberal democracy and denounce any compromise with capitalism. March sees four major subgroups within contemporary European far-left politics: communists, democratic socialists, populist socialists and social populists.
Hloušek and Kopeček add secondary characteristics to those identified by March and Mudde, such as anti-Americanism, anti-globalization, opposition to NATO and rejection of European integration.