Tour Charlemagne, Romanesque tower in Tours, France

Tour Charlemagne is a square tower of rough light-gray masonry, the surviving north transept tower of the former Basilica of Saint Martin. Its flat top replaced a 56-meter spire demolished in 1794. A pointed-arch relief of a mounted figure sits near the top above two narrow arched openings, and a round-arched portal opens at the base.

The tower was added in the second half of the 11th century over the north arm of the transept of the Romanesque Basilica of Saint Martin, consecrated on 4 July 1014. A Gothic storey with pointed-arch windows was added in the early 14th century, and a 56-metre spire existed by the 17th century. The basilica was demolished from 1797 to 1803, but the tower was kept after a restoration project was proposed in 1805. It partly collapsed in 1928.

The name refers to Luitgarde of Alemannia, Charlemagne's fourth wife, who died in Tours on 4 June 800 during the emperor's stay. Tradition holds she was buried under or near the building, but the tomb has never been identified. The tower is the last remnant of the Basilica of Saint Martin besides the Tour de l'Horloge.

The tower stands on Rue des Halles in Old Tours, its lower section framed between the street and neighbouring buildings; the round-arched portal at its base is the feature to look for. It is a classified monument since 13 September 1958, and the south side lost the transept that once buttressed it, so the masonry is best seen from the street rather than from above.

The tower survived demolition of the basilica in 1797–1803 only because a 1805 restoration project was planned to recall Napoleon's coronation as a new Charlemagne; the project was never carried out. It later housed a joinery, a 107-metre artesian well was sunk at its foot in 1831, and a water tank weighing 218 tonnes sat on its first floor from 1860 to 1885. Weakened, it partly collapsed in 1928.