Ottawa/Macdonald–Cartier International Airport (IATA: YOW, ICAO: CYOW) is the main international airport serving Ottawa, Ontario, Canada, and its metropolitan area as well as Gatineau, Quebec known as the National Capital Region. It is named after the Canadian statesmen and two of the "founding fathers of Canada", Sir John A. Macdonald and Sir George-Étienne Cartier. Located 5.5 nautical miles (10.2 km; 6.3 mi) south of downtown Ottawa in the south end of the city, it is Canada's sixth-busiest airport, Ontario's second-busiest airport by airline passenger traffic, with 4,095,914 passengers in 2023. The airport is a home base for Canadian North (formerly First Air) and a hub for Porter Airlines.

It is classified as an airport of entry by Nav Canada, and is staffed by the Canada Border Services Agency. It is one of eight Canadian airports that have United States border preclearance facilities. The airport was formerly a military base known as CFB Ottawa South/CFB Uplands, and is still home to the Royal Canadian Air Force's (RCAF) 412 Transport Squadron, which provides air transport for Canadian and foreign government officials.