Oak Grove Fork Clackamas River is a 21-mile (34 km) tributary of the Clackamas River in the U.S. state of Oregon. From its headwaters in the Warm Springs Indian Reservation near Abbot Pass in the Cascade Range, the river flows generally west through Mount Hood National Forest in Clackamas County to the unincorporated community of Ripplebrook. Here it enters the main stem of the Clackamas River.