The Basilica dei Santi Bonifacio e(d) Alessio is a church on the Aventine Hill in Rome, Italy, dedicated to Saint Boniface of Tarsus and Saint Alexius. Founded between the 3rd and 4th centuries, it was restored in 1216 by Pope Honorius III (some columns of his building survive in the present building's eastern apse), in 1582, in the 1750s by Tommaso De Marchis (his main altar survives), and between 1852 and 1860 by the Somaschi. The 16th century style facade, elaborated from the De Marchis phase, is built onto the medieval-style quadriportico.
The church has a Romanesque campanile. On the south side of the nave is the funerary monument Eleonora Boncompagni Borghese of 1693, to a design of Giovan Contini Batiste and in the south transept the Chapel of Charles IV of Spain, with an icon of the Assumption of the Madonna dating from the 12th century, thought to have been brought back from the east by St Alexius. The church also contains the tombstone of Peter Savelli (of the same family as Honorius).
A Romanesque crypt survives below the church, whose main altar contains relics of St Thomas of Canterbury. It has a 12th-century wall of frescoes of the Agnus Dei and symbols of the Four Evangelists, along with one in the north aisle of St Gerolamo Emiliani introducing orphans to the Virgin by Jean Francois De Troy, and at the end of the aisle The Holy Steps and the titular church of Saint Alexius in wood and stucco by Andrea Bergondi.
The basilica has been a cardinal title church from 1587. In 1587 it was called Sant'Alessio. In the 19th century the former dedication of the basilica was renewed, so from that time on the official name of the basilica and the cardinal title are Santi Bonifacio e Alessio.