The Upper Germanic Limes, also called Rhaetian Limes or simply "the Limes", was the border between the Roman Empire and the unsubdued Germanic peoples.

The Limes extended from Koblenz on the Rhine to Eining (close to Kelheim) on the Danube. The total length was 568 km. It included at least 60 castles and 900 watchtowers.

The first emperor who began to build fortifications along the border was Augustus, shortly after the devastating Roman defeat in the Battle of the Teutoburg Forest in 9 A.D.. Originally there were numerous Limes walls, which were then connected to form the Upper Germanic Limes along the Rhine and the Rhaetian Limes along the Danube. Later these two walls were linked to form a common borderline.

The Limes was not an insurmountable bulwark. There were numerous apertures in order to enable trade between Romans and Germanic tribes.

Germanic invasions in the late 3rd century led to the abandonment of the Limes.