Cornelius Castoriadis (French: [kastɔʁjadis]; Greek: Κορνήλιος Καστοριάδης [kastoriˈaðis]; March 11, 1922 ke December 26, 1997) was a Greek-French philosopher, social critic, economist, psychoanalyst, author of The Imaginary Institution of Society, and co-founder of the Socialisme ou Barbarie group.