Bear Brook is a tributary of the Millstone River in central New Jersey in the United States.
Bear Brook starts at , near exit 8 on the New Jersey Turnpike. It flows west, crossing the New Jersey Turnpike and Route 130 and flowing through the Bear Brook Park Acquisition. It turns northeast to join another tributary and continues flowing northwest, receiving more tributaries. It crosses CR-571 (Princeton Hightstown Road) and Clarksville Road before draining into the Millstone River at , near Princeton Junction.