Methods and apparatus for cooling mirrors in an extreme ultraviolet (EUV) lithography system using a liquid metal interface are described. According to one aspect of the present invention, an apparatus includes a heat exchanger, a mirror assembly, and a first liquid metal interface. The heat exchanger includes at least one well defined therein. The mirror assembly includes a mirror block having a mirrored surface. The mirror assembly also has at least one surface. Finally, the first liquid metal interface includes liquid metal which is contained in the first well. The at least one surface is in contact with the liquid metal to transfer heat from the mirror block to the heat exchanger.