Rihanna will serve as a guest judge on the upcoming singing competition 'The X Factor,' giving creator Simon Cowell his latest big name addition as he attempts to compete with similar programs 'American Idol' and 'The Voice.'

TMZ says the 'Cheers (Drink to That)' singer will be one of the guest judges who will help the show's four mentor/judges -- Cowell, Paula Abdul, Nicole Scherzinger and L.A. Reid -- decide which contestants to select. The site says Rihanna enjoyed working on the finale of the UK version of 'The X Factor' last season and is eager to appear on the American show.

Also likely to appear on the upcoming season is Mariah Carey. Cowell pursued Carey for months and evidently finalized a role for her, although she reportedly missed an important taping due to Hurricane Irene. With the judges' extensive connections within the music industry, we bet that Rihanna and Mariah are just the beginning in a long line of superstars who end up on the show.

With the first episode set to air in less than two weeks, 'The X Factor' has been ramping up its promotional efforts, releasing a series of ads teasing the upcoming season. The show premieres on FOX on Wednesday, September 21 at 8PM EST.