Bell tower of San Martino, Romanesque bell tower in Piazza San Martino, Lucca, Italy

The bell tower of San Martino rises at the south corner of Lucca Cathedral's facade, its lower third dating before the 12th century. It stands 59.5 metres on a square verrucano base and shows five orders of openings: single, double, triple and two levels of four-light windows, topped by Ghibelline merlons.

The lower third of the tower predates the 12th century. From the mid-13th century, work resumed using limestone from the San Lorenzo quarries at Vaccoli on Monte Pisano, and construction likely ended in the early 14th century, when the two largest bells were cast between 1320 and 1324 under operai Matteo Campanari and Bonaventura Rolenzi. The 1204 cathedral facade was built around the pre-existing tower, leaving its portico asymmetrical.

The tower's bells form a concert of seven in E-flat 3, some of them cast in the 13th and 14th centuries; the two largest were made between 1320 and 1324 under the works overseer Matteo Campanari and his successor Bonaventura Rolenzi. The cathedral bell tower stands at the south corner of the facade, and its presence forced the asymmetric design of the 1204 frontispiece.

The tower is reached by 217 steps, and the climb to the top is only possible since the restoration completed in 2016. The bell tower is part of the visit route of the cathedral's museum and archaeological complex, together with the cathedral, the Museo della cattedrale, the baptistery and the archaeological area of Santi Giovanni e Reparata, all on piazza San Martino.

The tower was repeatedly struck by lightning, as recorded in the account books of the Opera di S. Croce with entries for "spese per accomodare il campanile per danno fatto dalla saetta". A restoration completed in 2016 clarified its construction phases and now allows visitors to climb to the top.