"Waking Up in Vegas" is the fourth official single released from Katy Perry's album, One of the Boys. It was written by Katy Perry, Desmond Child and Andreas Carlsson. It is produced by Greg Wells and co-produced by Perry. Wells is credited with playing all the instruments on the song. It was officially released to US radio stations on April 21, 2009

The music video was shot by Joseph Kahn in Las Vegas on March 26, 2009. It made it's premiere when released on April 28, 2009 on the Australian, UK and U.S. iTunes store. It begins with Perry holding hands with her love interest played by Joel David Moore as he places a single coin in a slot machine. Moore is victorious as hundreds of coins pour rapidly out of the machine. It then cuts to a scene as Perry plays a game of poker wearing a red showgirl costume, defeating Daniel Negreanu then to her with Moore joyfully holding many money notes. The two lovers are then escorted to the Palms hotel. Katy kicks out Penn & Teller from her hotel suite. Katy begins to win poker over and over again as there are quick cuts of her along with Moore racing through the streets of Vegas each with a yellow and black Lamborghini Murciélago. There is also another scene where Katy and Moore are in their own Chariots driven down a Vegas street with an Elephant and fire blower beside. The couple are then found kissing in a money booth. After the kiss Katy's luck changes and she begins to argue with Moore. The video closes with what began the video. Moore once again places a single coin in the slot machine and is victorious.