Watertown International Airport (IATA: ART, ICAO: KART, FAA LID: ART) is in the Town of Hounsfield in Jefferson County, New York, United States, 6 mi (5.2 nmi; 9.7 km) west of Watertown. The airport is used for general aviation, but has scheduled passenger service subsidized by the Essential Air Service program. The airport has no scheduled international passenger flights, but is available as an international port of entry for private aircraft on two hours' advance notice from pilots.

The Federal Aviation Administration says this airport had 2,203 passenger boardings (enplanements) in calendar year 2010, 4,449 in 2011, and 16,988 in 2012. It is included in the Federal Aviation Administration (FAA) National Plan of Integrated Airport Systems for 2023–2027, in which it is categorized as a non-hub primary commercial service facility.

On July 12, 2024, a Boeing C-17 Globemaster III from the 732nd Airlift Squadron landed at Watertown International Airport and stayed for two days before leaving.

As of April 5th, 2025, the airport was undergoing a series of construction to add a new jet bridge, terminal, and baggage claim.