St. Clair County International Airport (IATA: PHN, ICAO: KPHN, FAA LID: PHN) is a public airport owned by the government of St. Clair County, Michigan, United States. It is located in Kimball Township, five miles (8 km) southwest of the central business district (CBD) of Port Huron. It is included in the Federal Aviation Administration (FAA) National Plan of Integrated Airport Systems for 2017–2021, in which it is categorized as a regional reliever airport facility.