Lottery is a game in which players pay a small amount of money, select groups of numbers, or have machines spit out random combinations, and win a prize if enough of their number matches the winning combination. Although the casting of lots to make decisions or determine fate has a long record (including several instances in the Bible), public lotteries for material gain are more recent, with the first recorded one held during the reign of Augustus Caesar for municipal repairs in Rome, and the first to distribute prize funds publicly known to be a lottery in Bruges, Belgium, in 1466. Lotteries are popular with politicians because they raise money for a variety of public usages through a process that is viewed as painless and voluntary (in contrast, taxes are generally perceived as a painful tax).

Although the disutility of a monetary loss from a lottery ticket can outweigh the entertainment value or other non-monetary benefits, most people consider a ticket purchase a rational choice if the expected utility of such a ticket exceeds the cost of buying it. This concept of relative value is a central idea in economics.

State-sponsored lotteries are common worldwide, generating large amounts of revenue and promoting legal gambling. However, critics argue that they also increase addictive gambling behavior and are a major regressive tax on lower-income households; that they divert resources from other pressing government needs, such as education; that they encourage corruption in politics and law enforcement; and that their operations are difficult to regulate.