"O" is a song from American R&B singer Omarion. It was released on July 17, 2004 as the first single off his debut album of the same name. "O" was the first choice for Omarion's debut single in the UK and was picked over "Touch", which was the original choice for his first UK single. The song was Omarion's first hit as a solo artist, peaking at number 27 on the Billboard Hot 100 and peaked at numbers 24 and 12 on the Mainstream Top 40 and Hot R&B/Hip-Hop Songs charts respectively. The song also charted in New Zealand and the UK, peaking at numbers 18 and 47 respectively. The song was also included on the 2005 compilation album Now That's What I Call Music! 18.