Loos () is a commune in the Nord department in northern France (Hauts-de-France).
It is located in the European Metropolis of Lille, and is a suburb of the city of Lille, bordering it on its southwest side. As of 2023, the population of the commune was 22,567. The commune has a land area of .
The Hôtel de Ville, with its large belfry, was inscribed on the UNESCO World Heritage List in 2005 in recognition of its historical importance to municipal power in Europe.
The Kennedy Tower, the tallest tower in the region, was demolished in July 2025.
Loos is twinned with Geseke, Germany.