Named after the place Saint-Michel, at the north end of the boulevard of the same name.
The square is named after the pont Saint-Michel, which took the name in 1424 from the nearby chapel of Saint-Michel in the royal palace. It was cut through in 1855 with the boulevard and officially named in 1864. The station curves under the square from the rue Danton to the Seine, beneath an unusually high vault of 12.5 metres.