Porta San Donato, Medieval city gate in Bologna, Italy.

Porta San Donato is a brick gate tower with defensive battlements that formed part of Bologna's third defensive ring. It still stands as an important landmark connecting different parts of the medieval city layout.

Porta San Donato was first built in the 13th century in brick, with quarters for guards beside it. A drawbridge was added in 1354; the gate was walled up and made unusable in 1428, then reopened and remodelled in the 15th century with a rivellino. Between 1952 and 1959 more than a metre of wall was demolished to ease vehicle flow from the ring roads into via San Donato, against the opinion of the Direzione Generale delle Antichità e Belle Arti. Restoration work followed between 2007 and 2009.

The gate marks the threshold to Bologna's university quarter and reflects how the city remained a hub of learning over many centuries. Visitors passing through this point enter one of Europe's most historically important academic zones.

The gate is easily accessible on foot while exploring the old city, with no barriers preventing a close view of its brick facade and tower. It can be quickly visited as part of a walk along the remaining defensive walls circuit.

The gate retains a fortified outwork from the 15th century known as a rivellino, which was designed to repel attackers approaching the main entrance. This forward defensive element is one of the few of its kind still visible in the city.