The Monadnock Mills are a historic mill complex in Claremont, New Hampshire. They extend along the southern bank of the Sugar River on both sides of Water Street, between the Broad Street bridge to the east, and the junction of Main and Water Streets in the west, where they abut the industrial area formerly associated with the Sullivan Machinery Company; there also a small number of surviving elements on the north side of the river opposite this area. The complex represents the surviving elements of what was once the largest manufacturing complex in the upper Connecticut River watershed area, and one of its oldest. The mills were listed on the National Register of Historic Places in 1979. Many of its buildings have been repurposed to other uses.