Appleton International Airport (IATA: ATW, ICAO: KATW, FAA LID: ATW), formerly Outagamie County Regional Airport, is an airport located in Greenville, Wisconsin, United States, 3 nautical miles (5.6 km; 3.5 mi) west of Appleton. It is included in the Federal Aviation Administration (FAA) National Plan of Integrated Airport Systems for 2025–2029. Along with Madison’s Dane County Regional Airport, it is one of two airports in the State of Wisconsin categorized as a small hub. The airport covers 1,638 acres (6.63 km2) at an elevation of 918 feet (280 m) above sea level.

It is the third busiest of eight commercial airports in Wisconsin in terms of passengers served. In 2016 the airport contributed $676 million to the Northeastern Wisconsin economy. In May 2018, Appleton International Airport was the fourth fastest growing airport in the US. It is the main base of privately owned regional airline Air Wisconsin and was the original home of Midwest Airlines. Midwest Airlines grew out of Kimberly-Clark subsidiary K-C Aviation, which was sold in 1998 to Gulfstream Aerospace, which retains a major facility at the airport, focusing on maintenance, interior completions, and exterior painting for the company's G600, G650, and G700 products.

The airport attracts people heading back and forth between the EAA's AirVenture, Air Academy and other programs in nearby Oshkosh. Starting in 2017, the airport began to offer camping for AirVenture.