Fabrication of Au mesh structures by reactive-monolayer-assisted thermal nanoimprint lithography was demonstrated. A fluorescent dye-doped polystyrene thin film on a Au-plated substrate modified with a photoreactive monolayer was transformed using a mold with a lattice pattern. Au mesh patterns were obtained by removal of the residual layers and subsequent wet etching. The aperture ratio could be tuned by controlled side-etching. Au mesh structures with a Au line width of approximately 1 mu m are promising for transparent conductive substrates.