Showbiz
Rex Features
The 26-year-old confirmed that she is expecting her first child with the film producer earlier this month.
She has been dating Warren since he worked as a director's assistant on the set of her 2004 movie Fantastic Four, although they separated briefly during the summer.
Her publicist Brad Cafarelli announced the engagement after the actress was spotted wearing a diamond ring over the Christmas break.
He told the Associated Press in an email: "I can confirm that they are engaged."
A source close to the couple recently claimed that Alba does not want to get married while she is pregnant.
More: Showbiz
More Showbiz News
Ten Things About...
Ten Things About... Ridley ScottWe find out ten fast facts about the English producer and director.
Interviews
'Angels' Share' Ken Loach interviewKen Loach, Paul Laverty and Paul Brannigan on their whiskey-soaked comedy.
Fashion & Beauty
Duchess of Cambridge's memorable momentsFlick through a gallery of Kate Middleton's stand-out public appearances.
Celeb Birthdays
Marilyn Monroe: Life and career in picsFlick through our gallery on what would have been Marilyn's 86th birthday.
