Gambling involves wagering something of value on an event that is based in some way on chance, with the expectation of winning something else of value. It is a common activity around the world, with total gambling revenue of approximately $335 billion in fiscal year 2021 (excluding state and local lottery revenues). Gambling is a major international commercial enterprise and is subject to various taxes in some countries. Unlike cigarette or alcohol taxes, gambling revenues are typically used to support programs to help people with problem gambling.

Gamblers gamble on a variety of events, from sports and politics to lottery drawings and scratchcards. The stakes are usually money, although other things can be wagered as well, such as merchandise, collectible games, and other materials with a specific market value. Historically, gambling has been associated with social problems and crime, from legal forms of betting to swindling and cheating. Despite this, it is a popular pastime with many enthusiastic proponents and strong opponents.

Those who struggle with compulsive gambling often have difficulty recognizing their addiction, because they frequently rationalize and deceive themselves. This often leads to secretive behavior and lying about their gambling, attempting to conceal their addictive behaviors from friends and family. People with gambling disorders may also have underlying mood disorders like depression, anxiety or bipolar disorder, and treatment for these conditions can improve their ability to control their gambling habits. Treatment options include cognitive-behavioral therapy, which teaches people to recognize and challenge unhealthy gambling behaviors, and inpatient or residential treatment for those with severe problem gambling.