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 which may be used in an EUV lithography system includes a heat exchanger, a mirror assembly, and a first liquid metal interface. The heat exchanger including at least a first surface. The mirror assembly includes a first mirror block having a first mirrored surface, as well as at least a first well. Finally, the first liquid metal interface includes liquid metal which is contained in the first well. The first surface is in contact with the liquid metal such that heat may be transferred from the first mirror block to the heat exchanger.