Seattle–Tacoma International Airport (IATA: SEA, ICAO: KSEA, FAA LID: SEA) is the primary international airport serving Seattle and its metropolitan area in the U.S. state of Washington. It is in the city of SeaTac, which was named after the airport's nickname “Sea–Tac”, approximately 14 miles (23 km) south of Downtown Seattle and 18 miles (29 km) north-northeast of Downtown Tacoma. The airport is the busiest in the Pacific Northwest region of North America and is owned by the Port of Seattle.

The entire airport covers an area of 2,500 acres (3.9 sq mi; 10 km2) and has three parallel runways. The airport has flights to cities throughout North America, Oceania, Europe, the Middle East, and Asia. It is the primary hub for Alaska Airlines, whose headquarters are near the airport. It is also a hub and international gateway for Delta Air Lines, which has expanded at the airport since 2011. As of 2022, 31 airlines operate at SEA, serving 91 domestic and 28 international destinations.

In 2023, Sea-Tac served 50,887,260 passengers, 2 percent below the all-time record set in 2019.