Tulln an der Donau is a town in the Austrian state of Lower Austria, and the seat of the Tulln district. Because of its abundance of parks and other green spaces, Tulln is often referred to as Blumenstadt, meaning city of flowers. While the town is surrounded by the Tullnerfeld flatland, almost all of its built-up area is located on the southern bank of the Danube.
Tulln is one of the oldest towns in Austria. Although it was settled in pre-Roman times (the name Tulln is presumably a Celtic word), it gained importance as the Roman fort of Comagena (Comagenis). In the final years of Roman rule, Saint Severinus of Noricum is said to have visited the city, saving it from the Barbarians.