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. Capellen is home to the NATO Support and Procurement Agency which acts as the headquarters of NATO's Agencies.