Schlösschen Gundeldingen, Medieval castle in Gundeldingen district, Switzerland.

Schlösschen Gundeldingen is a castle complex in Basel featuring red-painted facades and multiple connected sections along Dittingerstrasse. A distinctive external staircase tower from 1674 characterizes its appearance, and the interior now contains office spaces for government departments and private businesses following a 1974 renovation.

Gundeldingen began as four related castles, not a single 14th-century complex: the Upper Middle Castle was built in the mid-14th century and first mentioned in 1377 as a fief of Saint Alban Monastery, while the Lower Middle Castle was built around 1400 and the Outer Castle at the end of the 14th century. The Inner Castle followed in the 16th century as a merchant's manor. The Upper Middle Castle was demolished in the 19th century for a brewery, the Outer Castle after 1953 for flats at Gundeldingerstrasse 446; the Lower Middle Castle, sold to the city hospital in 1842, was saved by a 1965 committee and reopened in 1974.

The name Gundeldingen covers four once-separate castles, of which only parts of two survive. The Lower Middle Castle, built around 1400, was bought in 1549 by Thomas Platter, first rector of the Basel Gymnasium, who repaired the dilapidated building until his death in 1582. Since 1974 its main building has housed government and private offices.

The building is partially accessible since it functions as an active office building with restricted interior access. It is best to view the exterior architecture and the distinctive tower from the street while exploring the surrounding neighborhood.

A mineral spring discovered on the grounds in 1704 provided water to the local community until around 1800. This source was an important resource for the neighborhood before gradually falling into disuse.