The Le Mans Congress was the twenty-first national congress of the French Socialist Party (Parti socialiste or PS). It took place from November 18 to 20, 2005.

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The objective of the Congress was to solve internal divisions created by the French referendum on the European Constitution and designate a new leadership at all levels.

Five motions were presented to be voted upon by members:

• For a liberal socialism: Truth and Action (Pour un socialisme libéral : vérité et action): Social liberal current led by Jean-Marie Bockel, PS mayor of Mulhouse.
• Rally the Left (Rassembler à gauche): Left-wing motion led Laurent Fabius, and supported by Jean-Luc Mélenchon and Marie-Noëlle Lienemann. This was the first time since the 1990 Rennes Congress that Fabius led a motion.
• Socialists, for success on the left: Will, Truth, Unity (Socialistes, pour réussir à gauche : Volonté - Vérité - Unité): Majority motion led by François Hollande, supported by the party elites: Martine Aubry, Dominique Strauss-Kahn, and Bertrand Delanoë.
• New Socialist Party-For a Socialist Alternative (Nouveau Parti Socialiste-Pour une Alternative Socialiste): Left-wing motion supported by Vincent Peillon, Arnaud Montebourg, Benoît Hamon, Michel Vauzelle, Henri Emmanuelli.
• Utopia: Alterglobalization current led by Franck Pupunat.

Hollande was re-elected as First Secretary unopposed. He won 76.96% of the votes.^[1]