Cheshire County is a county in the southwestern portion of the U.S. state of New Hampshire. Its county seat is the city of Keene. Cheshire was one of the five original counties of New Hampshire, and is named for the county of Cheshire in England. It was organized in 1771 at Keene. Sullivan County was created from the northern portion of Cheshire County in 1827.
According to the U.S. Census Bureau, the county has an area of 729 square miles (1,890 km), of which 707 square miles (1,830 km) is land and 22 square miles (57 km) (3.1%) is water. The highest point in Cheshire county is Mount Monadnock, in the northwestern part of Jaffrey, at 3,165 feet (965 m).