Bonner Stadtbefestigung, Medieval fortification remains in Bonn, Germany.

Bonner Stadtbefestigung is a defensive system begun in 1244 with a medieval wall ring, later extended by baroque bastions. Surviving elements include the Alter Zoll, a former bastion on the Rhine, and the Sterntor, rebuilt in 1900 with parts of the wall and a semicircular tower. The wall's course is marked by Kasernenstraße and Theaterstraße.

The walls began construction after 1244 under Archbishop Konrad von Hochstaden as city protection. Later, four main gates and additional harbor entrances along the Rhine were added to protect the growing trade city.

The Alter Zoll is not a watchtower but a former bastion of the baroque fortifications on the Rhine bank, built from 1642 on the site of a Renaissance customs building; in the 18th century it was popular as a "Schlossterrasse". The Sterntor is a 1900 reconstruction, assembled at Bottlerplatz two years after the original gate tower was demolished, and it incorporates parts of the medieval wall and a half-round tower. The gate's name derives from the Pisternenstraße, the bakers' street, from Latin pistrina.

The fortification remains are easily walkable and follow a route through the city center, especially along Theater Street. Information panels at various locations explain the function and age of each section.

Parts of the medieval counter-wall are now integrated into the pedestrian zone and serve visitors as natural seating. This everyday use connects the historic stones directly to modern city life.