Nordertor, City gate in Flensburg, Germany

The Nordertor is a stone city gate in Flensburg, northern Germany, marking the former northern entrance to the city. It features stepped gables on both sides and shows building details typical of early 17th-century North German Renaissance construction.

The present gate replaced the Norderpforte, a checkpoint about 100 metres further south, and was built around 1595, though sources give 1595 or 1596. It marked the northern edge of the built-up town until 1796, when building outside the walls was permitted and the Neustadt suburb grew north of it. From 1881 residents and councillors sought its demolition as a traffic obstacle; instead the adjoining Nackestift was torn down around 1890 and the road rerouted east around the gate, which survived.

The gate displays royal emblems on its northern face showing the coat of arms of King Christian IV alongside the city's own heraldic symbols. These marks of authority remain a notable visual feature of the passage today.

The gate stands along a main road and can be seen freely from outside at any time of day. The passage is open to walk through, and the stonework is easy to look at up close on both sides.

In 1966, the gate appeared on a West German postage stamp worth 30 Pfennig, with over 3 billion copies printed. That makes it one of the most widely produced stamp images in German postal history.