Porta Magna - San Petronio, Gothic portal at San Petronio Basilica in Bologna, Italy

Porta Magna is the central portal of the Basilica of San Petronio in Bologna. Jacopo della Quercia carved ten Genesis reliefs on the doorposts, eighteen prophets in the splay, and a lunette with the Madonna and Child with Saints Ambrose and Petronius, completed by Varignana. The architrave holds five New Testament scenes, and the central arch prophets are by Antonio Minello and Antonio da Ostiglia, except the Moses by Amico Aspertini.

Jacopo della Quercia began the portal's decoration in 1425 for papal legate Louis Aleman, but work stopped in 1434, before the sculptor's death in 1438, leaving it without a cusp. In 1510 Arduino Arriguzzi moved the portal forward. Michelangelo later studied the Genesis panels and praised the Madonna as the most beautiful of the Quattrocento.

The lunette holds Jacopo della Quercia's Madonna and Child with Saints Ambrose and Petronius, the latter finished by Varignana. Michelangelo called the Madonna "the most beautiful Madonna of the Quattrocento". The eighteen prophets in the splay are by Jacopo, except the central Moses, carved by Amico Aspertini; the arch prophets are by Antonio Minello and Antonio da Ostiglia.

The portal sits at the basilica entrance facing Piazza Maggiore and is easily visible and accessible from the square. Visitors get the best view of the carved details by standing directly in front of the doorway, where light hits the relief panels.

The young Michelangelo Buonarroti studied the sculptural techniques of Jacopo della Quercia at this portal and drew inspiration from the style for his own works. This artistic connection makes the location a key point in the development of Renaissance sculpture.