Lacq (French pronunciation: [lak]; Occitan: Lac) is a commune in the Pyrénées-Atlantiques department in southwestern France. On 1 January 2024, the former commune of Urdès was merged into Lacq.

It lies just northwest of the prefecture (department capital) Pau.

In modern times the local economy has been based on the industrial use of subsurface petroleum reserves, and since 1951 on the extraction and development of a very large natural gas reservoir underneath the city. Processing of the large quantities of hydrogen sulfide in the gas have made Lacq a center of sulfur production.