Named after the rue Saint-Placide, after Saint Placidus, a disciple of Saint Benedict.
Placidus, born around 515 into an old Roman family, was entrusted as a boy to Benedict at Subiaco and followed him to Monte Cassino. The station opened in 1910 as Rue de Vaugirard and was renamed on 15 November 1913, to avoid confusion with the Vaugirard station on the North–South line, now line 12.