Denver International Airport (IATA: DEN, ICAO: KDEN, FAA LID: DEN), locally known as DIA, is an international airport in the Western United States, primarily serving metropolitan Denver, Colorado, as well as the greater Front Range Urban Corridor. At 33,531 acres (52.4 sq mi; 135.7 km2), it is the largest airport in the Western Hemisphere by land area and the second largest on Earth, behind King Fahd International Airport. Runway 16R/34L, with a length of 16,000 feet (3.03 mi; 4.88 km), is the longest public use runway in North America and the seventh longest on Earth. The airport is 25 miles (40 km) driving distance northeast of Downtown Denver, 19 miles (31 km) farther than the former Stapleton International Airport, the facility DEN replaced: the airport is actually closer to the City of Aurora than central Denver, and many airport-related services, such as hotels, are located in Aurora.

Opened in 1995, DEN currently serves 25 different airlines offering non-stop service to over 215 destinations throughout the Americas, Europe, and Asia; it was the fourth airport in the U.S. to exceed 200 destinations. The airport is a major hub for United Airlines and the largest operating base for both Frontier Airlines and Southwest Airlines. With over 40,000 employees, the airport is the largest employer in Colorado. The airport is located on the western edge of the Great Plains and within sight of the Front Range of the Rocky Mountains.

In both 2021 and 2022, DEN was the third busiest airport in the world as well as the third busiest airport in the United States by passenger traffic. In 2023, it was the sixth busiest airport in the world and remained the third busiest airport in the United States having served around 77.8 million passengers, more than a 12% increase from the prior year.