New Hampshire Route 9 (abbreviated NH 9) is a 109.910-mile-long (176.883 km) state highway located in southern New Hampshire, United States. It runs across the state from west to east and is a multi-state route with Vermont and Maine, part of 1920s-era New England Interstate Route 9. The western terminus of NH 9 is at the Vermont state line in Chesterfield, where it connects to Vermont Route 9. Its eastern terminus is at the Maine state line in Somersworth, where it connects to Maine State Route 9.