Jamesburg is a Borough in Middlesex County, New Jersey, United States. As of the United States 2000 Census, the borough population was 6,025.
Jamesburg was formed as a borough by an Act of the New Jersey Legislature on March 19, 1887, when it was created from portions of Monroe Township, based on the results of a referendum held on March 15, 1887. Jamesburg's incorporation was confirmed April 15, 1915.
Jamesburg is located at 40°21′00″N 74°26′21″W / 40.350107°N 74.439095°W / 40.350107; -74.439095 (40.350107, -74.439095).