Roundup Airport (IATA: RPX, ICAO: KRPX, FAA LID: RPX) is a public use airport located two nautical miles (4 km) north of the central business district of Roundup, a city in Musselshell County, Montana, United States. It is owned by the city and county. This airport is included in the National Plan of Integrated Airport Systems for 2011–2015, which categorized it as a general aviation facility.