The 'Obsessed' singer has reportedly landed a £15,000-a-week contract to appear in an unnamed production in London's West End theatre district from next spring.
A source told Britain's Daily Mirror newspaper: 'Mariah's done a bit of acting in her time but nothing on this scale.
'She was hugely flattered to have been asked and is determined to nail the part. She is pretty confident in her own abilities.
'And although there has been talk of musicals, Mariah has always wanted to star in a play so this really is a dream come true.'
This is not the first time Mariah has been linked with a British theatre role.
In 2005, it was reported she was house-hunting in the UK to find a base while she was appearing in a musical version of 'The Prince And The Showgirl' but the role never materialised.
The following year, Mariah revealed plans to create a Christmas musical using tracks from her 1994 album 'Merry Christmas'. The script was set to be penned by 'High School Musical' writer Peter Barsocchini.
It was claimed in 2008 that the 39-year-old star's life story is to be made into a musical.
A source said: "A huge, huge Broadway producer is interested in Mariah's story and it's in discussions.'