Aurora is Colorado's third-largest city. The municipality is split between Arapahoe and Adams County, with a small portion lying in Douglas County. The city and its western neighbor are the principal cities of the Denver-Aurora metropolitan area. As of the 2000 Census, the city population was 276,900. The latest Census estimates place the city's population at 291,843, making it the 61st-largest in the United States. The city will soon reach the milestone of 300,000 residents.

In 1891, Donald Fletcher founded a town on the plains east of Denver and named it after himself. The real estate tycoon ran out two years later, leaving the new residents with bond payments for non-existent water. The town was renamed Aurora (Latin for dawn) in 1907, and remained a small community until after World War II. Postwar suburban development transformed the town into what became the fastest growing city in the United States during the late 1970s and early 1980s.

Although Aurora has long been considered by many only as one of Denver's larger suburbs, its growing population in recent decades (now over half the size of the City of Denver) has led to efforts for co-equal recognition with its larger neighbor. A former mayor once expressed the somewhat whimsical notion that eventually the area would be called the "Aurora/Denver Metropolitan Area." However, such efforts are somewhat hampered by the lack of a large, historically important central business district in the city, which is largely suburban in character.

World attention focused on Aurora for seven weeks during the fall of 1955, as President Dwight D. Eisenhower recovered from a heart attack at Fitzsimons Army Medical Center. The hospital is also the birthplace of 2004 Democratic presidential candidate John Kerry. Decommissioned in 1999, the facility is now under redevelopment as the campus of the University of Colorado Health Sciences Center and Hospital, which are relocating there from Denver, and the Colorado Bioscience Park Aurora. These facilities will employ a workforce of 32,000 at build-out.

In 2004, Aurora was honored as the Sports Illustrated magazine's 50th Anniversary "Sportstown" for Colorado because of its exemplary involvement in facilitating and enhancing sports. Aurora's active populace is also reflected in the variety of professional athletes hailing from the city (see Notable People from Aurora below). Aurora's first professional sports franchise, the Aurora Cavalry in the International Basketball League, began play in 2006.

In 2005, Aurora again made headlines because the city is planning to split from three counties to create the City and County of Aurora. The plan was originally created back in 1996 and it was defeated by Aurora voters while Broomfield successfully split from four counties to create the second city-county in 2001.