The actress, 28, whose mother was born in Glasgow, is believed to have married the musician yesterday, in a small town-hall ceremony in the south of France, with just a handful of friends and relatives present.
Knightley, who first found fame in Bend It Like Beckham and has since appeared in the Pirates Of The Caribbean films as well as Pride And Prejudice, Anna Karenina and Atonement, wore a short strapless off-white dress with a tulle skirt and a jacket said to be by Chanel.
Her new husband, the keyboardist in indie rock band Klaxons, wore a dark blue suit and a pale blue skinny tie for the occasion.
The pair were seen happily skipping from the ceremony in sunglasses, drenched in the French sunshine.
Knightley - the face of Chanel’s Coco Mademoiselle perfume - completed her relaxed, chic look with a garland of flowers around her head and ballet pumps.
Local mayor Aime Navello told the Daily Mail he carried out the 30 minute ceremony in French with the help of a translator.
“As is customary, I asked Keira first if she would accept James,” he said.
“We had wondered whether they might reply ‘I do’ like the English. In fact, as we posed the question in both French and English, they both replied with a ‘Oui’ and a ‘Yes’.
“Keira was a charming bride, very modest and simple in her attitude, as was James. I got the impression that it was a very moving experience for both of them.”
The couple, who became engaged last summer and have recently moved to a multi-million pound home in East London, left the ceremony in Mazan, near Avignon, to the applause of their 11 guests and were ushered into a silver Renault Clio.
A reception is believed to have taken place at Knightley’s mother Sharman Macdonald’s nearby estate, with guests reported to include actress Sienna Miller and designer Karl Lagerfeld.
In an interview last month, Knightley said she did not want an extravagant wedding day. She said: “We’re not big wedding types. I don’t need to have all that. I’m just trying to enjoy the engagement bit.”
The pair were introduced to each other by mutual friend, TV presenter Alexa Chung, after Knightley split up from her boyfriend of five years, Pride And Prejudice co-star Rupert Friend.
Oscar-nominated Knightley recently appeared on the Sunday Times Rich List with a fortune of £30 million. Later this year she can be seen in comedy Can A Song Save Your Life? and thriller Jack Ryan.