branches off. The municipality had a population of in , and covers an area of {{Dutch municipality total area Alphen aan den Rijn|km2|abbr=on}} of which {{Dutch municipality water area Alphen aan den Rijn|km2|abbr=on}} is water.

The municipality of Alphen aan den Rijn also includes the communities of Aarlanderveen, Benthuizen, Boskoop, Hazerswoude-Dorp, Hazerswoude-Rijndijk,