Las Vegas is the most populous city in Nevada, United States. The city was founded in the first decade of the 20th century, and is a major vacation, shopping, and gambling destination. In the 2000 census, the city reported a population of 478,434. The Census Bureau's official population estimate as of 2004 was 534,837. Las Vegas has been the county seat of Clark County since its formation in 1909. Recent figures place the population for the Las Vegas metropolitan area, which includes all of Clark County, at around 1,950,000 people (2005 estimate), the fastest growing in the United States.

The name Las Vegas is often applied to the unincorporated areas of Clark County that surround the city, especially the resort areas on and near the Las Vegas Strip. This 4½ mi (7¼ km) stretch of Las Vegas Boulevard is mostly outside the Las Vegas city limits, in the unincorporated town of Paradise.

The center of gambling in the US, Las Vegas is sometimes called Sin City due to the popularity of legalized gambling, availability of alcoholic beverages any time (like all of Nevada), various forms and degrees of adult entertainment, and legalized prostitution in nearby counties (it is illegal, though, in Las Vegas and Clark County; Nevada law prohibits prostitution in counties which have populations greater than 400,000). The nickname favored by local government and promoters of tourism is The Entertainment Capital of the World. The city's glamorous image has made it a popular setting for films and television programs.