River Forest lies along the Des Plaines River to the west and is bordered by Illinois Route 43 to the east and Illinois Route 64 to the north. Along with the Des Plaines River, much of the western boundary of River Forest consists of the Thatcher Woods forest preserve of Cook County and the Des Plaines River Trail. According to the 2010 census, River Forest has a total area of , of which (or 99.92%) is land and (or 0.08%) is water.
