The Koppelpoort is a medieval gate - part of the second city wall of Amersfoort - which was built between 1380 and 1425. It combines a land and water-gate, which is unique in the Netherlands. The gate was attacked in 1427 during the siege of the city, but was repelled. The name Koppelpoort refers to an area outside the gate, which was called De Koppel. Travellers could be allowed or refused to enter through this combined gate, even if they were travelling over water. In addition, the water levels in the inner city could be regulated with it.

The Koppelpoort did get its current appearance during the restoration by well known Dutch architect Pierre Cuypers in 1885 and 1886. The latest restoration was completed in 1996. Nowadays the Koppelpoort is one of the eye catchers of Amersfoort.