Trenton–Mercer Airport (IATA: TTN, ICAO: KTTN, FAA LID: TTN) is a county-owned, joint civil–military, public airport located four miles northwest of Trenton in the West Trenton section of Ewing Township, Mercer County, New Jersey. Formerly known as Mercer County Airport, the airport serves one scheduled airline plus general and corporate aviation. The U.S. Department of Transportation reports that approximately 301,000 passengers arrived and 300,000 departed at the airport in the 12 months ending July 2023, for a total of 601,000 passengers.

With an average of 308 aircraft operations per day, Trenton–Mercer is the third-busiest airport in New Jersey after Newark Liberty International Airport's 1,228 per day and Teterboro Airport's 477 per day. As of May 2018, Trenton was the fifth fastest growing airport in the US.

The Federal Aviation Administration (FAA) National Plan of Integrated Airport Systems for 2023–2027 categorized it as a non-hub primary commercial service facility.