Henniker is a town located in Merrimack County within the state of New Hampshire, United States. It sits along the Contoocook River at the junction of New Hampshire Route 114 and Old Concord Road. The municipality lies fully within the Merrimack River watershed and is bordered by Warner, Hopkinton, Weare, Deering, Hillsborough, and Bradford.

The area was originally known as Number Six before being granted to Andrew Todd in 1752. Settled in 1761 by James Peter, it was incorporated in 1768 by Governor John Wentworth and named for Sir John Henniker. The town later hosted a unique sign language community due to high rates of congenital deafness in the nineteenth century.

The main village, defined as the Henniker census-designated place, contains the Edna Dean Proctor Bridge built in 1835. Craney Hill in the south is home to the Pats Peak ski area, while the highest point is an unnamed summit near the northwestern corner. The town also includes the village of West Henniker.

Henniker functions as a college town and resort area featuring skiing and white-water kayaking. It is home to New England College and the Pats Peak Ski Area. The game of paintball originated in the town in 1981, and tourism has been attracted by the river's scenic beauty since the late 1800s.

The total population was 6,185 as of the 2020 census, with 3,166 residents in the CDP. The town is crossed by U.S. Route 202 and state routes 9 and 114. It maintains a free library, two community centers, and educational institutions including Henniker Community School and John Stark Regional High School.