The Nashua River Rail Trail is a state park and recreation area in Ayer, Massachusetts. It is another rail to trail project developed by the Massachusetts Department of Conservation and Recreation.

The Nashua River Rail Trail traces its roots back to 1848, when the railroad was created as a part of the Worcester & Nashua Railroad. It connected the towns of Worcester and Nashua initially and then extended to Portland, Maine in 1874. It was acquired by the DCR in 1987 and was opened and dedicated on October 2002.

The Nashua River Rail Trail runs for 11 miles and travels along a flat, scenic landscape. It provides access to many opportunities to spot wildlife and passes through a wide variety of natural habitats like swamps, ponds, woods, wetlands, and even a farmland.