Seattle-Tacoma International Airport (IATA: SEA, ICAO: KSEA, FAA LID: SEA), also known as Sea-Tac Airport, is located between Seattle and Tacoma, Washington, United States.

In 2012, the airport served over 33.2 million passengers. The top-five carriers at the airport in number of passengers carried between December 2011-November 2012 were Alaska Airlines (39.07%), Horizon Air (12.88%), Delta Air Lines (10.26%), United Airlines (9.94%) and Southwest Airlines (9.74%).

Sea-Tac is at the intersections of State Route 518, State Route 99 and State Route 509. It is located about 1.5 miles (2.4 km) from Interstate 5. It serves Seattle, Washington and Tacoma, Washington as well as western Washington state. The airport is a hub for Alaska Airlines, whose headquarters is located near the airport, and its regional subsidiary Horizon Air. The airport has service to several destinations throughout North America, Europe and East Asia.

The airport has a Central Terminal building with four concourses (A–D) and two Satellite Terminals (North and South). The satellite terminals are connected to the central terminal by an underground people mover system.. There are three main checkpoints at Sea-Tac and a fourth that is opened as needed during peak periods.