One of the Boys is the second studio album by American singer Katy Perry. It was released on June 17, 2008, by Capitol Records. She collaborated on the album with producers Greg Wells, Dr. Luke, Dave Stewart, Max Martin, and Ted Bruner among others, and wrote most of the songs in collaboration with other producers and writers. Perry wrote its title track along with "Thinking of You" and "Mannequin" alone, with "Thinking of You" being written back in 2002. The extended play (EP) Ur So Gay (2007), containing her song of the same name (later released as a promotional single), was released before One of the Boys to generate interest in the singer and the then-upcoming album.
One of the Boys is Perry's first album under the stage name Katy Perry, following her debut Katy Hudson (2001), which was released under her real name on Red Hill Records. One of the Boys received mixed reception from critics, with some deeming it as being filled with "potential hits" and others criticizing the material they perceived to be weak. Commercially, it charted within the top ten in Argentina, Austria, Canada, Denmark, France, Germany, Ireland, Mexico, Norway, Switzerland, and the United States. One of the Boys earned Perry two Grammy Award nominations, and has sold seven million copies worldwide. It has been certified Diamond in Brazil as well as multi-platinum in Australia, Canada, Chile, Denmark, Finland, France, New Zealand, Norway, the United Kingdom, and the United States.