Mezmerize is the fourth album by System of a Down and the first half of the Mezmerize/Hypnotize double album. It was released on May 17, 2005, six months before Hypnotize. Despite the time difference between releases, the album actually takes its name from the lyrics in the song Hypnotize; Mezmerize and Hypnotize were recorded within the same time frame. The album features guitarist Daron Malakian sharing most of the vocal work with vocalist Serj Tankian, splitting the vocals at least halfway on most of the tracks.

The album debuted at number one in at least twelve countries, including the US Billboard 200, and has since been certified Platinum by the RIAA. It was also chosen as one of Amazon.com's Top 100 Editor's Picks of 2005. The album has sold over 2.5 million copies worldwide since it's release.