Herseler Werth, Protected nature reserve in Bornheim, Germany

Herseler Werth is a 1,678.5-metre-long, 14.8-hectare Rhine island at kilometre 660.80 L, near Hersel in Bornheim between Bonn and Cologne. The flat island is planted throughout with poplars set by hand after the Second World War. Since 1993 it has been a nature reserve and may not be entered.

Between 1202 and 1237 a major breach of the Rhine to the west washed away parts of Hersel and the old Roman road between Bonn and Cologne, and the Herseler Werth emerged from that event. The island lies at Rhine kilometre 660.80 L and is 1,678.5 metres long.

The island's name, Werth, is the local Rhenish word for a river island. On the Herseler shore at its southern end stands the boathouse of the Herseler Wassersport-Verein 1930 e.V., a canoeing club founded in 1930 that still paddles these waters.

The island has been a nature reserve since 1993 and may not be entered, so it can only be viewed from the Herseler bank or from a boat on the Rhine. The current between the island and the Hersel shore is unusually strong, and a teenager drowned there while swimming in 2004. The boat house of the Herseler Wassersport-Verein 1930 e. V. stands at the southern end on the Hersel bank.

On 27 October 2009, a 500-kilogram World War II aerial bomb was found during bank work at low water beside the island, not by divers. It could not be defused and was detonated in a controlled explosion after Hersel, Uedorf, Rheidt and Mondorf were evacuated.