Sports betting is the general activity of predicting sports results by making a wager on the outcome of a sporting event. Perhaps more so than other forms of gambling, the legality and general acceptance of sports betting varies from nation to nation. In the United States, for example, sports gambling is only legal in Nevada casinos, while in many European nations bookmaking (the profession of accepting sports wagers) is highly regulated but not criminalized. Proponents of legalized sports betting generally regard it as a hobby for sports fans that increases their interest in particular sporting events, thus benefiting the leagues, teams and players they bet on through higher attendances and television audiences.

Opponents fear that, over and above the general ramifications of gambling, it threatens the integrity of amateur and professional sport, the history of which includes numerous attempts by sports gamblers to fix matches, although proponents counter that legitimate bookmakers will invariably fight corruption just as fiercely as governing bodies and law enforcement do. Most sports bettors are overall losers as the bookmakers odds are fairly efficient. However, there are professional sports bettors that make a good income betting sports.

The Internet not only revolutionized the ability to bet online, but also the ability to communicate with like-minded bettors. Sports betting forums offer lively give and take where bettors discuss their predictions about games and help one another decide on profitable bets. Additionally a cottage industry of tipster sites has sprung up where inexperienced bettors can, for free or a fee, receive previews and tips for upcoming events. Free sites are generally affiliated with online bookmakers and finance their service by introducing new customers to their preferred online bookmakers.