Reichenstein Castle, Medieval castle in Arlesheim, Switzerland

Reichenstein Castle is a high medieval spur castle on a rocky spur of the Reichensteiner Berg at 460 m above sea level, northeast of Arlesheim's village centre in the canton of Basel-Landschaft. A residential tower with four storeys is joined on the south by a slightly taller keep whose walls are 2 m thick; a lower house was added later. The compact complex is protected by rock faces and a natural dip to the south.

The castle appears in written records for the first time in 1239, already belonging to the Reich von Reichenstein family. They held it for over five centuries before it changed hands in the early 1800s.

The castle's name comes from the Reich family, who held it as a fief from the Bishop of Basel from 1245; between 1250 and 1400 five generations of Reichs sat on Basel's council and supplied the city six mayors and a bishop, Peter Reich (1286–1296). Today the foundation that runs the castle rents it out for weddings, family parties, meetings and even civil marriage ceremonies for up to 50 people.

The castle is reached by car or on foot from Arlesheim, turning off at the height of Birseck Castle on the road to Schönmatt. A wooden bridge and a castle gate lead into the courtyard, from which a partly rock-cut entrance opens into the residential tower. The tower room above the knights' hall gives a wide view over the Birstal, the Vosges and as far as the Black Forest.

Reichenstein is one of four fortresses that once stood in a row along the Birseck slope, forming a defensive line together. Having so many fortified structures this close to each other is rare in Switzerland.