Only Girl (In The World) shifted nearly 1,700 copies last week, which was enough to break the milestone. The single was originally released more than a year ago and topped the charts in November 2010. It is Rihanna's first solo song to sell a million copies and the 108th single to do so in UK chart history.
The singer has previously passed the seven-figure mark as a guest artist. Eminem's Love The Way You Lie, which featured Rihanna's vocals on the chorus, sold its millionth copy earlier this year. Only Girl (In The World) is only the 15th single by a female artist to reach a million sales.
The most recent was Someone Like You by Adele. Lady Gaga, Alexandra Burke, Leona Lewis and Kylie Minogue have also previously crossed the million sales mark. Rihanna's latest single, We Found Love, recently spent six weeks at the top of the UK singles chart. The 23-year-old's new album, Talk That Talk, recently beat One Direction to number one on the album chart.
Rihanna has sold more than 12 million singles in the UK since the release of her debut single in August 2005. She is the only artist to achieve that many sales in such a short space of time.