Burgstall Regenstauf, Medieval castle ruins in Regenstauf, Germany.

Burgstall Regenstauf is a vanished hilltop castle on the Schlossberg at 436.6 m above sea level near the Schlossberg inn in Regenstauf, Bavaria. The site is recorded as a monument partly as a well house (D-3-75-190-73) and as a medieval tower mound (D-3-6838-0103). A 1500 picture shows a castle-like building next to a ruined tower, possibly the former keep.

Regenstauf was a seat of the Burgraves of Regensburg, a family from the Babonen line; Burgrave Otto appears as Comes de Stowfe in 1125, and the castle must have been built before that date. After the last Babonen died in 1195/96 the site passed to the Wittelsbachs, and a 1205 treaty records Ludwig I holding castrum Stouffe. In 1504 the Palatine knight von Eyb destroyed the castle during the Landshut War of Succession.

The name Regenstauf comes from the Old High German stauf or stouf, a cone-shaped hill by the Regen. The Babenberg counts appended it to their title: Otto appears in 1125 as Comes de Stowfe. The site is recorded as a Turmhügel, a tower mound, of the high or late Middle Ages, and is listed as a Bodendenkmal.

The site is accessible through marked hiking paths and cycling routes that connect to the Regental cycle network. Good footwear is recommended since the terrain is hilly and can become slippery, especially after rain.

The 1471 sale by Heinrich Zenger to Duke Albrecht distinguished between a decayed Burgstall and a still-standing Schloss, and a 1500 picture shows a ruined tower beside the castle, possibly the former bergfried. The site is also recorded as a Turmhügel of the high or late Middle Ages.