Mamer is a commune and town in south-western Luxembourg. It is located 7 km (4.3 mi) west of Luxembourg City. The commune includes both Mamer itself and the smaller communities of Capellen and Holzem. Mamer is situated on the river Mamer, a tributary of the Alzette. The A6 motorway from Luxembourg to Brussels, also designated European route E25, runs through Mamer.

Capellen is a town in the commune of Mamer, in south-western Luxembourg, 12 km west of Luxembourg City. As of 2023, the town has a population of 2,371. Despite not having a commune named after it, Capellen lends its name to the canton of Capellen, and is the only town in Luxembourg to bear the latter distinction but not the former.