Trajan's Bridge (Romanian: Podul lui Traian; Serbian: Трајанов мост, romanized: Trajanov most), also called Bridge of Apollodorus over the Danube, was a Roman segmental arch bridge, the first bridge to be built over the lower Danube and one of the greatest achievements in Roman architecture. Though it was only functional for 165 years, it is often considered to have been the longest arch bridge in both total and span length for more than 1,000 years.

The bridge was constructed in 105 AD by Emperor Trajan's architect Apollodorus of Damascus before the Second Dacian War to allow Roman troops to cross the river. Fragmentary ruins of the bridge's piers can still be seen today.