Waking Up in Vegas

"Waking Up in Vegas" is a song by American singer Katy Perry, released as the fourth and final single from her second studio album, One of the Boys (2008). Perry wrote the song with Desmond Child and Andreas Carlsson, and Greg Wells produced it, who is also credited for playing all the instruments on the song. It was officially released to US radio stations on April 21, 2009. "Waking Up in Vegas" is a pop rock track about an underage couple getting drunk and blowing their money in Las Vegas, paying homage to the phrase "what happens in Vegas, stays in Vegas."

The song received positive reviews from music critics, who complimented its catchiness, and attained commercial success, reaching the top ten in eight countries. It peaked at number nine and became Perry's third top ten single in the United States, whilst also reaching number one on the Mainstream Top 40 sub-chart and on Hungarian radio. The music video was directed by Joseph Kahn and it features Perry and actor Joel David Moore in Vegas partying and gambling. Perry performed the track during her Hello Katy Tour and California Dreams Tour, and an acoustic snippet was sung during the Las Vegas show of Witness: The Tour. The song was used to promote Perry's concert residency at Resorts World Las Vegas, which began in December 2021.