DD-WRT is Linux-based firmware for wireless routers and access points. Originally designed for the Linksys WRT54G series, it now runs on a wide variety of models. DD-WRT is one of a handful of third-party firmware projects designed to replace manufacturer's original firmware with custom firmware offering additional features or functionality.

Sebastian Gottschall, a.k.a. "BrainSlayer", is the founder and primary maintainer of the DD-WRT project. The letters "DD" in the project name are the German license-plate letters for vehicles from Dresden, where the development team lived. The remainder of the name was taken from the Linksys WRT54G model router, a home router popular in 2002–2004. WRT is assumed to be a reference to 'wireless router'.

Buffalo Technology and other companies have shipped routers with factory-installed, customized versions of DD-WRT. In January 2016, Linksys started to offer DD-WRT firmware for their routers.