Cathedral of Our Lady of the Assumption, Romanesque cathedral in Acqui Terme, Italy.

The cathedral of Our Lady of the Assumption stands on Piazza Duomo, its facade preceded by a 17th-century neoclassical portico of paired sandstone columns with three serliana arches. The Gothic bell tower of 1479 rises to its right, and five Romanesque apses with small arched windows close the rear. The interior, remodelled in Baroque style, has three naves under cross vaults.

Construction began under Bishop Primo (989–1018) and the cathedral was consecrated on 11 November 1067 by Bishop Guido, now the city's patron saint. Lombard masters built it as a Romanesque Latin-cross church with a projecting transept and three naves, expanded to five in the 18th century. The Gothic bell tower was finished in 1479 and the Pilacorte portal dates from 1481.

The cathedral is dedicated to the Assumption of the Virgin Mary and is the seat of the Bishop of Acqui, whose bishopric has existed since at least the 4th century. Bishop Guido, who consecrated the building in 1067, is venerated as patron saint of the city and diocese; his Baroque altar stands in the transept, and a 1496 panel shows him with the four Doctors of the Church.

Entry is typically free and the church is open to visitors during the day. It is advisable to wear respectful clothing and to be mindful of any religious services happening while you are inside.

The 11th-century crypt beneath the raised presbytery is divided into small aisles by 98 marble columns, and on its left pier survives a fresco of Saint Anthony Abbot from around 1400. Four side altars stand around the central altar, which carries a modern tabernacle.