.lu is the Internet country code top-level domain (ccTLD) for Luxembourg. .lu domains are administered by Restena. Since February 1, 2010, the administrative contact no longer needs to be based in Luxembourg.

For many years, the application for .lu domains were done only via postal mail or fax. The fees for a .lu second level domain are €40 for the creation (or modification of a contact) and €40 yearly (including VAT). On September 18, 2006, the registry introduced a domain name registrar model. While the classic paper registration is possible, registering with a certified registrar is preferred.