Zwammerdam is a village in the Dutch province of South Holland along Oude Rijn river. It is a part of the municipality of Alphen aan den Rijn, and lies about 6 km southeast of Alphen aan de Rijn. The name derives from a dam built in the Rhine river in 1165 AD by Count Floris III of Holland, to protect the land stream downwards from floods.

The Oude Rijn is a branch of the Rhine delta in the Dutch provinces of Utrecht and South Holland, starting west of Utrecht, at Harmelen, and running by a mechanical pumping station into the North Sea at Katwijk. Its present-day length is 52 kilometres.