Thermes Napoléon is a monumental French thermal spa complex named after Emperor Napoleon III. The building recalls an era when thermal baths were visited not only for their believed healing properties but also served as important social gathering places for the wealthy.

In 1856, Emperor Napoleon III commissioned the construction of a new and luxurious spa complex. On July 22, 1857, he personally laid the foundation stone. Four years later, in 1861, the building opened its doors. The complex combined thermal treatments with a Grand Hôtel, allowing guests to stay overnight and enjoy the baths without leaving the building.

The impressive structure was built from beige and pink sandstone. Its 55-metre-long central hall was inspired by the ancient Roman Baths of Caracalla. An imperial eagle above the entrance, marble statues and richly decorated galleries reflected the grandeur of the French Second Empire.

In 1932 and 1933, the complex underwent extensive renovations. On April 10, 2001, important parts of the building were protected as a historic monument, including its façades, roofs, central hall and several original treatment rooms.

After more than a century and a half, thermal spa activities finally came to a halt in 2025. This marked the end of a long history of therapeutic bathing in a building that once symbolised imperial luxury and the golden age of French spa culture.