Born into a middle-class family in the Paris suburb of Meudon in 1937, Mr Jospin is a member of France's small Protestant minority, a community with a reputation for diligent austerity.
In 1963 he went to the elite Ecole Nationale d'Administration (ENA), where he became a Trotskyist. Inducted into the Internationalist Communist Organisation (OCI) he took the code-name Comrade Michel.
This came back to haunt him after he became prime minister in 1997, not because he had been on the revolutionary left - which in 1960s France was not unusual - but because he later lied about it.
He has still not denied claims that he fed information to the OCI after joining Francois Mitterrand's Socialists in 1971.
His circle of friends remains that of the left-bank artists and "intellos". His wife, Sylviane Agacinski, is a feminist philosopher with a son by the world-renowned structuralist Jacques Derrida.
Successively Socialist Party secretary and education minister, Jospin came to be identified in the early 1990s with a current in the party that was critical of Mitterrand's last years as president - tainted by charges of corruption and political dishonesty - and as a result he was chosen as candidate to run against Gaullist leader Jacques Chirac in 1995.
The result was a narrow defeat, avenged two years later when, following Mr Chirac's disastrous dissolution of parliament, Mr Jospin led the left to victory and became prime minister.
|SI\' a l\'economia de marcaa, NO\' alla socitaa de marcaa.|