Stony Brook is a central New Jersey stream and a tributary of Green Brook. Rising near Watchung at Hillcrest Road and Interstate 78, it follows a winding path through Watchung and North Plainfield to Green Brook Park on the Plainfield town line. Its course shifts from southeast to southwest, then northeast into Watchung Lake, where two unnamed feeder streams join it. Leaving the lake, it continues through Watchung, cuts through the Stony Brook Gorge in the First Watchung Mountain, and drops over Wetumpka Falls. Farther downstream it crosses Route 22, receives Crab Brook, its only named tributary, then turns south to meet Green Brook.