Trecento Palace (Palazzo dei Trecento), also called the Palace of Reason (Palazzo della Ragione), is one of the most important buildings in the historic center of Treviso, overlooking Piazza dei Signori.
The palace was built around 1185 as a board room of the various organs of the city of Treviso (Domus comunis) replacing the old building near the cathedral; the palace was completed in 1268, when a prison was adjoined.