The former Hollyoaks star will replace Girls Aloud’s Kimberley Walsh as the royal-with-a-secret Princess Fiona from 21 May.
Stenson is the latest new cast member to join the musical adaptation of the hit Dreamworks film, after Dean Chisnall and Neil McDermott replaced original stars Nigel Lindsay and Nigel Harman earlier this year.
Comedian, singer and actor Richard Blackwood, who plays Donkey, is now the only member of the original quartet of lead performers still treading the fairytale boards at the Theatre Royal Drury Lane.
Shrek, which has been running in London since 6 May 2011, follows the story of a grumpy ogre who is forced to go on a quest by the diminutive Lord Farquaad. Along the way, he discovers there is more to life than guarding your own patch of mud.
The show, which originally starred Amanda Holden as Fiona, has proved so popular with West End audiences that it has also extended its booking period, with tickets now available until 31 March 2013.