The phrase "What happens in Vegas, stays in Vegas" is a popular saying that originated as a marketing slogan for the city of Las Vegas. It implies that whatever experiences, behaviors, or events occur while someone is in Las Vegas should remain private and not be shared or discussed outside the city. The phrase plays on the reputation of Las Vegas as a place known for its vibrant nightlife, casinos, and party atmosphere, suggesting that people can let loose and have fun without the consequences following them home.

It has since evolved into a widely recognized idiom, often used humorously to suggest that what happens in a specific situation should remain confidential or not be brought up later.