Ithan Creek is a tributary of Darby Creek in Delaware County, Pennsylvania, in the United States. It is approximately 4.2 miles (6.8 km) long and flows through Radnor Township and Haverford Township. The creek's watershed has an area of 7.39 square miles (19.1 km2) and is highly developed. It has three named tributaries: Browns Run, Kirks Run, and Meadowbrook Run.

Darby Creek is a tributary of the Delaware River in Chester, Delaware and Philadelphia counties, in the U.S. Commonwealth of Pennsylvania. It is approximately 26 miles (42 km) long. The watershed of the creek has an area of 77.2 square miles (200 km2). It has twelve named direct tributaries, including Cobbs Creek, Little Darby Creek, Ithan Creek, and Muckinipattis Creek. The creek has a low level of water quality for most of its length. The lower Darby Creek area was deemed a Superfund site by the U.S. Environmental Protection Agency (EPA) due to contamination with dangerous chemicals from two landfills.