Millbrook is a locality in the Adelaide Hills, outside Adelaide, South Australia. It borders Inglewood to the north and Cudlee Creek to the south. It is home to a state primary school and small hamlet settlement, connected to Cudlee Creek.The original township within the valley was demolished to make way for the Millbrook Reservoir.Buildings at this location included a small private school and a hotel. These people moved into the Cudlee Creek area when the reservoir works began in 1914. The former township of Chain of Ponds was removed due to the possible reservoir's impact upon the settlement.