Monmouth Junction is an unincorporated community and census designated place (CDP)[9] in South Brunswick Township, Middlesex County, New Jersey, United States.

[13] Monmouth Junction is in southwestern Middlesex County, in the western part of South Brunswick Township.

It is bordered to the northwest by Heathcote, to the northeast by Deans, and to the east by Dayton, all within South Brunswick as well.

U.S. Route 1 forms a small part of the community's western border.

The 2010 United States census counted 2,887 people, 903 households, and 801 families in the CDP.

Of all households, 9.9% were made up of individuals and 2.8% had someone living alone who was 65 years of age or older.

[13] As of the 2000 United States Census[6] there were 2,721 people, 870 households, and 736 families living in the CDP.

[17] People who were born in, residents of, or otherwise closely associated with Monmouth Junction include: