The Imperial Palace at Gelnhausen, in German also called the Kaiserpfalz Gelnhausen, Pfalz Gelnhausen or Barbarossaburg, is located on the Kinzig river, in the town of Gelnhausen, Hesse, Germany.

It was founded in 1170, and like the town whose creation was closely linked to the palace, goes back to Emperor Frederick I (Barbarossa). The palace enabled the expansion of imperial territory along an important long-distance highway, the Via Regia.

The exact date when construction of the palace began is still very much disputed by historians. Debate revolves around the question of whether the building of the palace took place a few years before the official founding of the royal town in 1170. or whether there was even an earlier castle belonging to the Counts of Selbold-Gelnhausen (de). Various data acquired through the use of dendrochronology point to the time around 1170, in which the subsoil was made capable of bearing load by driving oak piles into the ground for the foundations of the walls.

The construction of the palace was probably managed by the Counts of Büdingen (de), who erected the castle of Büdingen as their own residence nearby.

In 1180, the imperial palace at Gelnhausen was the venue for the great imperial court or Hoftag of Gelnhausen, at which Henry the Lion was put on trial in his absence and his imperial fiefs redistributed. In the years that followed, further imperial courts were convened at Gelnhausen. Whether at this time the now ruined palas had been built for use as an assembly hall is not clear, but appears likely. The large number of different stonemasons suggests a relatively large number of labourers working on the building site at the same time and thus a rapid pace of construction.

During the Hohenstaufen era, the palace was an Imperial Castle (Reichsburg), had a burgrave and Burgmannen. Its estate included Büdingen Forest (de), in which the castle's occupants still retained timber rights (for construction and firewood) until the 19th century. The decline of the palace began as early as the 14th century when, in 1349, Emperor Charles IV (HRR) enfeoffed it, together with the town, to the Counts of Schwarzburg and never reclaimed it. In 1431, the Count of Hanau and Count Palatine Louis III procured the palace and town from Count Henry of Schwarzburg. At the end of the 16th century, the Counts of Isenburg in Birstein had taken over the burgrave's office, but did not reside at the castle. During the Thirty Years' War, the town and palace were severely damaged and Imperial and Swedish troops razed down its main building.

After the extinction of the House of Hanau in 1736, Gelnhausen fell to the Landgraves of Hesse-Kassel. The palace was then used as a quarry until 1811. The castle chapel had to be partly demolished due to its dilapidated condition. Around 1810, the palace became one of the first buildings from the epoch of Romanesque architecture in Germany that attracted the interest of art-loving scholars.

At the end of the 19th century and during the 20th century, the first safety measures were carried out to preserve the remains of the palace for posterity. Likewise, it was not until the end of the 19th century that the previously independent municipality of Burg was dissolved and integrated into the town of Gelnhausen.

Today, the palace belongs to the state of Hesse and is managed by the Administration of State Castles and Gardens for Hesse. Along with its attached castle museum, it is open to the public.