The Thermes de Cluny (French pronunciation: [tɛʁm də klyni]) are the ruins of Gallo-Roman thermal baths lying in the heart of Paris' 5th arrondissement, and which are partly subsumed into the Musée national du Moyen Âge - Thermes et hôtel de Cluny.
The best preserved room is the frigidarium, with intact architectural elements such as Gallo-Roman vaults, ribs and consoles, and fragments of original decorative wall painting and mosaics.
It is believed that the bath complex was built by the influential guild of boatmen of 3rd-century Roman Paris or Lutetia, as the consoles on which the barrel ribs rest are carved in the shape of ships' prows.
The spectacular frigidarium is entirely incorporated within the museum and houses the Pilier des Nautes (Pillar of the Boatmen).
Although somewhat obscured by renovations and reuse over the past two thousand years, several other rooms from the bath complex are also incorporated into the museum, notably the gymnasium, which now forms part of gallery 9 (Gallery of French Kings and sculptures from Notre Dame that were taken down during the iconoclasm of the French Revolution).