The Uffizi museum in Florence said Monday it was suing French fashion house Jean Paul Gaultier for "unauthorised use" of Botticelli's "The Birth of Venus", its Italian Renaissance masterpiece.
Painted by Sandro Botticelli in the mid-1480s, it shows the nude goddess Venus standing on a giant scallop shell, covering her loins with her long blonde hair.
Gaultier used the image "on several garments, photos of which it published on its website and social networks," the Italian museum said.
It attached screenshots in which one model can be seen wearing a pair of trousers with part of the Venus painting printed on the rear.
Stretched across the buttocks is the part of the scene featuring the god Zephyr, who is blowing wind.
Other items being sold by Gaultier, famous for its cheeky designs, include a 150-euro Venus scarf and a 590-euros Venus dress.
Gaultier used the painting "without permission" and failed to pay rights, the Uffizi Galleries said, adding that it would seek damages.
A letter sent to the luxury fashion house in April had been ignored, it added.
The museum demanded Gaultier take the items off the market, or sort out a financial accord.
The Uffizi is one of the world's great museums, housing works from some of the greatest painters of the Renaissance, from Botticelli to Leonardo da Vinci, Michelangelo, Raphael, Caravaggio and Titian.
Botticelli, who died in 1510, is best known for "The Birth of Venus" and "Spring", both of which the Uffizi owns.
Some museums around the world, including the Art Institute of Chicago, the Metropolitan Museum of Art in New York, and Amsterdam's Rijksmuseum, have released many of their works into the public domain, meaning they are no longer subject to copyright.