Most known for his work on autonomism, Negri founded the Potere Operaio (Worker Power) group in 1969 and was a leading member of Autonomia Operaia. He published highly influential books urging "revolutionary consciousness".
He was accused in the late 1970s of various charges including being the mastermind of the left-wing militant organization Red Brigades (Brigate Rosse), involved in the May 1978 kidnapping of Aldo Moro.
Although the court was unable to conclusively prove his ties, he was convicted in 1984 and sentenced (in absentia) to 30 years in prison. He was given an additional four years on the charge of being ‘morally responsible’ for the violence of political activists in the 1960s and 1970.
Negri fled to France where he taught at the Paris VIII (Vincennes) and the Collège international de philosophie, along with Jacques Derrida, Michel Foucault and Gilles Deleuze. In 1997, after a plea-bargain that reduced his prison time from 30 to 13 years, he returned to Italy to serve the end of his sentence.
Along with Althusser and Deleuze, he has been one of the central figures of a French-inspired Neo-Spinozism in continental philosophy of the late 20th and early 21st centuries.
In 2000, alongside Michael Hardt, he published the "Empire", a book that theorizes an ongoing transition from a "modern" phenomenon of imperialism, centered around individual nation-states, to an emergent postmodern construct created among ruling powers.
Being consistently hostile to the 20th century socialism and the Soviet Union, Negri gradually ended up being an apologist of modern social democracy, especially in the last decades of his life. In May 2005, he supported a "Yes" vote to the referendum on the proposed EU constitution held in France.
Having waived any characteristic of revolutionary marxist thought, in the end of his life he endorsed the social democratic group called "Democracy in Europe Movement 2025" (DiEM25) founded by former Greek Finance Minister Yanis Varoufakis.