Kuala Lumpur International Airport opened on June 27, 1998, replacing Subang International Airport, which had reached its capacity limits. It was built in four and a half years at a cost of approximately $3.5 billion, on a 100-square-kilometer site in the Sepang district of Selangor, roughly 45 kilometers south of the city it serves. The airport sits outside Kuala Lumpur proper, a geographic quirk that catches first-time visitors off guard.

Designed by Japanese architect Kisho Kurokawa, the main terminal building embodies what Kurokawa called the concept of symbiosis: an airport in the forest, a forest in the airport. The roof is a series of hyperbolic paraboloid shells referencing traditional Islamic domes, and the structure incorporates native vegetation in its central spaces, blending Malaysia's cultural and ecological identity into the architecture itself. It is a landmark in its own right, often mentioned alongside the Petronas Towers as one of Malaysia's defining built works.

The airport operates 2 terminals. The main terminal handles full-service carriers, with Malaysia Airlines (the national flag carrier) using KUL as its primary hub. A second terminal, klia2, opened in May 2014 to replace the earlier Low-Cost Carrier Terminal and now serves AirAsia and AirAsia X, among other budget carriers. The airport has 3 parallel runways, each approximately 4,000 meters in length. In 2023, it handled more than 47 million passengers and over 819,000 aircraft movements, making it the busiest airport in Malaysia by a wide margin and a central node in the broader Southeast Asian air network.