The 28-year-old star with wed musician fiancé in Nice in a 'small affair'.
There she will get hitched to her Klaxton guitarist James Righton, 29, according to newspaper The Sun.
The event is due to only be a small affair to be witnessed by family and close friends.
The happy couple got engaged in summer 2012 and began residing together in a multi-million pound East London house recently.
“Most of their friends will fly out for the wedding on Friday,” a source revealed.
“They’ve been planning it for a while but wanted something small and private. They could get married in total private in stunning surroundings.”
Keira spoke in March about potentially making a big deal of her special day.
She admitted that the idea of an extravagant time doesn’t appeal to her tastes.
“I could have six fake weddings. God, that would be expensive,” she joked.
“We’re not big-wedding types. I don’t need to have all that. I’m just trying to enjoy the engagement bit.”
Keira was in a relationship with her Pride & Prejudice co-star Rupert Friend for five years however they broke up in January 2011.
She was introduced to James, who is the keyboard player for the Klaxons James, by their mutual friend Alexa Chung.
Keira featured on this year’s Sunday Times Rich List which stated she is worth a huge £30million.