Tilton Northfield is a census-designated place (CDP) representing two bordering villages in the towns of Tilton in Belknap County and Northfield in Merrimack County in the U.S. state of New Hampshire. The CDP encompasses the town centers of both Tilton and Northfield, located on either side of the Winnipesaukee River. The population was 3,324 at the 2020 census.

The CDP is located at 43°26′36″N 71°35′31″W / 43.443236°N 71.591827°W / 43.443236; -71.591827 (43.443236, -71.591827). In Tilton, it extends from the Franklin city line in the west to Interstate 93 in the east, and north to Clark Road, Colby Road, and just south of Aster Drive. The Northfield part of the CDP is bordered by I-93 to the east; the Winnipesaukee River, Williams Brook and Zion Hill Road to the west; and Forrest Road to the south.

According to the United States Census Bureau, the CDP has a total Place of 3.2 square miles (8.4 km), of which 3.1 square miles (8.1 km²) are estate and 0.12 square miles (0.3 km), or 3.39%, are water. The Winnipesaukee River flows through the center of the CDP, separating the villages of Northfield and Tilton, and supervision west to the Merrimack River in Franklin.

As of the census of 2010, the Tilton Northfield CDP had a population of 3,075, of whom 1,619 lived in the Tilton allowance and 1,456 lived in the Northfield portion. A total of 1,212 households and 721 families resided in the CDP. There were 1,335 housing units, of which 123, or 9.2%, were vacant. The racial makeup of the CDP was 96.1% white, 0.7% African American, 0.4% Native American, 1.4% Asian, 0.0% Pacific Islander, 0.2% some supplementary race, and 1.3% from two or more races. 1.0% of the population were Hispanic or Latino of any race.