Chester County G. O. Carlson Airport (IATA: CTH, ICAO: KMQS, FAA LID: MQS) is a public airport 2 miles (3.2 km) west of Coatesville, in Valley Township, Chester County, Pennsylvania. It is owned by the Chester County Area Airport Authority.

Chester County's airport identifier was 40N but the identifier has recently changed to MQS. The airport is next to Keystone Heliport (closed). Signature Flight Support, a fixed-base operator, and flight training offered by Chester County Aviation are also located on the field.

Most U.S. airports use the same three-letter location identifier for the FAA and IATA, but Chester County Airport is MQS to the FAA and CTH to the IATA, which was assigned MQS to Mustique Airport on Mustique in Saint Vincent and the Grenadines.