San Sisto, Romanesque church building in Pisa, Italy.

San Sisto is a church on via Pasquale Paoli near Piazza dei Cavalieri, built of rough-hewn stone in the Pisan Romanesque style. Its tripartite façade has a mullioned window and blind arches running along the gable, with Islamic ceramic basins set into the stone. The interior has three naves and nine bays, with a wooden ceiling and an apse at the end of the central nave.

Built in 1087 on the site of the earlier San Pietro in Corte Vecchia, a Lombard and Carolingian power centre, the church was dedicated to Saint Sixtus because Pisan victories often fell on 6 August, his feast day. It was consecrated in 1133, after already serving as the seat of the commune's most important notarial acts. Despite alterations in the 15th, 17th and 19th centuries, it kept its medieval appearance; Baroque stuccoes were removed in the 1910s.

The church displays Islamic ceramic basins from the 10th-11th centuries and an Arabic inscription in Kufic script commemorating Emir al Murtadà, reflecting Pisa's medieval Mediterranean connections.

The church stands between Via Pasquale Paoli and Via Corsica, near Piazza dei Cavalieri. On 6 August at 6 PM a ceremony is held outside with a laurel wreath laid on the memorial plaque, followed by a historical oration and Mass inside.

Contains a wooden crucifix from around 1370 modeled after the Volto Santo from Lucca, considered one of the rare copies of this revered religious artifact in Italy.