Montmayeur castle, Medieval tower in Aime-la-Plagne, France.

The Tour de Montmayeur is a former fortified house in Aime, Savoie, consisting of a quadrangular dwelling with a square keep rising at its centre. The keep is 19.30 metres high, 9.55 metres per side, with walls 2.40 metres thick. A large round tower housing a spiral staircase was added in the 16th century against the keep and dwelling. The keep's top has reconstructed machicolations, some original on the south and west, and cruciform arrow slits.

The tower is cited in 1392, when Claude de Montmayeur received it in fief, and again in 1447 for Humbert de Montmayeur and his brother Claude; it appears to have belonged to the Villette family. It formed part of a defensive chain protecting the town of Aime, with the Tour du Maney, a square tower across the Ormente, and the round tower of Poëncet, all under the castle of Saint-Sigismond. The 16th century brought new rooms, a round stair tower and a rectangular dwelling. The keep and dwelling were partly listed as monuments historiques on 21 August 1983.

The name comes from the Montmayeur family, who held the tower as a fief from 1392, when Claude de Montmayeur received it, and again in 1447 for Humbert and his brother Claude. The tower guarded a toll bridge over the Isère, and its door and a keep window date to the late 15th or early 16th century.

The tower stands in the southern part of Aime's bourg, at the corner of rue de la Gare and the railway line, close to the bridge over the Isère. It is a roadside building in the town itself, not a hilltop ruin, so it is reached on foot along the street. Only the keep and the dwelling are listed as monuments historiques.

The keep's walls are 2.40 metres thick, and the corners, arch voussoirs and door jambs are built of rounded river stones taken from the Isère, set in lime mortar. Look for the cruciform gun loops pierced through the masonry, and the machicolations surviving on the south and west sides from the original construction.