Katz Castle, Medieval castle in Sankt Goarshausen, Germany

Katz Castle, originally Neukatzenelnbogen, is a compact spur castle above Sankt Goarshausen. Its small footprint is dominated by a bergfried that was originally 40 metres tall, protected by a neck ditch cut into the rock and a triangular outwork. The 19th-century residential building only vaguely recalls the former palas; medieval fabric survives in the keep ruin, parts of the uphill shield wall and the zwinger.

The Counts of Katzenelnbogen built the castle between 1360 and 1371, probably in response to the neighbouring Electoral-Trier castle Maus, begun in 1356. With Rheinfels across the Rhine it formed a toll barrier. In 1479 the castle passed to the Landgraves of Hesse; it was besieged in 1626 and 1647, damaged in 1692, and blown up by Napoleon in 1806. Ferdinand Berg had it rebuilt as a residence in 1896–98.

The castle's official name, Burg Neukatzenelnbogen (New Cat's Elbow), was shortened in everyday use to "die Katz" (the Cat), pairing it with Burg Maus (Mouse) nearby. In 1435 the Counts of Katzenelnbogen planted Riesling vines here, among the first recorded in the region. The castle and its setting also appear in the Belgian comic L'Orgue du Diable from Roger Leloup's Yoko Tsuno series.

Katz Castle is privately owned and cannot be visited; the grounds and buildings are closed to the public. The exterior can be seen from the opposite bank in Sankt Goar and from the riverside paths and boat trips on the Rhine. The castle stands above Sankt Goarshausen on a ledge looking downstream.

The 1896–98 rebuild by district administrator Ferdinand Berg, designed by the Cologne firm Schreiterer & Below, paid little attention to the medieval remains; the Rhine-side block only vaguely recalls the former great hall. Genuine medieval fabric survives in the keep ruin, parts of the uphill shield wall and the outer ward. The castle has been in Japanese private ownership since 1989.