Lewis Brook is a tributary of the Stony Brook in Mercer County, New Jersey in the United States. Lewis Brook starts at 40°19′45″N 74°47′45″W / 40.32917°N 74.79583°W, near the Pennington Shopping Center. It flows eastward, crossing North Main Street, before draining into the Stony Brook at 40°20′0″N 74°46′54″W / 40.33333°N 74.78167°W.