Naperville is a city in DuPage and Will Counties in the U.S. state of Illinois, within the Chicago metropolitan area. As of the 2000 census, the city had a total population of 128,358. A special census taken in 2008 showed the population to be 144,560. Naperville is the fifth largest city in the state, behind Chicago, neighboring Aurora, Rockford, and Joliet. Approximately 100,000 Naperville residents live in DuPage County, while about 50,000 reside in Will County. Naperville was one of the ten fastest growing communities in the United States during the 1990s.

As of 2008, Naperville is the 167th most populous city in the United States. According to the 2005 American Community Survey, there were an estimated 147,779 people, 48,655 households, and 37,143 families residing in the city. The population density was 4,162.8 inhabitants per square mile (1,607.3 /km2). There were 51,636 housing units at an average density of 1,454.5 per square mile (561.6 /km2). The racial makeup of the city was 80.2% White, 4.3% African American, 0.2% Native American, 12.3% Asian, 0.00% Pacific Islander, 1.26% from other races, and 1.48% from two or more races. Hispanic or Latino of any race were 5.4% of the population.

In 2008, the median household income in the city was $101,470, and the median family income was $123,485. The mean income for a family in Naperville was $153,340, according to the 2008 estimates. The per capita income for the city was $44,787. About 3.4% of the population was below the poverty line, including 2.8% of those under age 18 and 6.4% of those age 65 or over.