A nanoimprint process that presses a mold into a thin thermoplastic polymer film on a substrate to create vias and trenches with a minimum size of 25 nm and a depth of 100 nm in the polymer has been demonstrated. Furthermore, the imprint process has been used as a lithography process to fabricate sub-25 nm diameter metal dot arrays of a 100 nm period in a lift-off process. It was found that the nanostructures imprinted in the polymers conform completely with the geometry of the mold. At present, the imprinted size is limited by the size of the mold being used; with a suitable mold, the imprint process should mold sub-10 nm structures with a high aspect ratio in polymers. The nanoimprint process offers a low cost method for mass producing sub-25 nm structures and has the potential to become a key nanolithography method for future manufacturing of integrated circuits and integrated optics.