Colonia is an unincorporated community and census-designated place (CDP)[9] in Woodbridge Township, Middlesex County, New Jersey, United States.

The stretch was constructed on the west side of the Pennsylvania Railroad (now the Northeast Corridor) from near the northeast of Dow Avenue between Colonia and Iselin to Cedar Street in Menlo Park, to avoid two railroad crossings.

The old road is now Middlesex-Essex Turnpike and Thornall Street, on the east side of the tracks.

Colonia is in northeastern Middlesex County, in the northwest corner of Woodbridge Township.

It is bordered to the north by Clark, to the northeast by Rahway, to the east by Avenel, to the south by Iselin, and to the west by Edison.

[1] The community is drained to the northeast by the South Branch of the Rahway River, part of the watershed of the Arthur Kill.

Colonia has a humid subtropical climate (Cfa) and average monthly temperatures range from 33 °F (1 °C) in January to 78.1 °F (25.6 °C) in July.

[12] The Garden State Parkway passes through the western portion of the CDP but does not interchange there.

"[14] The 2010 United States census counted 17,795 people, 6,160 households, and 4,977 families in the CDP.

[16] As of the 2000 United States Census[6] there were 17,811 people, 6,184 households, and 5,077 families residing in the CDP.