Dean Brook is a river in Smithills, Bolton, Greater Manchester, historically within Lancashire. Dean Brook rises on Smithills Moor and flows in a south-easterly direction, through a deep valley called High Shores Clough. It collects Dakin's Brook at Barrow Bridge and then runs through Smithills before meeting Raveden Brook to form Astley Brook, which subsequently joins Eagley Brook and forms the River Tonge.