"Wanted to let the news out directly," Krasinksi tweeted. "Emily and I are so incredibly happy to welcome our daughter Hazel into the world today! Happy bday!"
British star Blunt, 30, and Office alum Krasinski, 34, began dating back in 2008 and became engaged in August 2009. They married on July 10, 2010 in Como, Italy.
The Devil Wears Prada actress was quite the picture-perfect mom-to-be throughout her pregnancy, frequently wearing very little makeup and showing off her natural glow. After exclusively revealing she was pregnant to Us Weekly back in September, Blunt continued filming the upcoming big-screen musical Into the Woods in the U.K. "Emily's so ready to have the baby!" a source told Us in December. "It's been difficult, with her traveling and them having to be apart."
An insider also told Us at the time that the spouses were finishing up the nursery and babyproofing. "John's trying to make the pregnancy as easy as possible for Emily," the source said of the Something Borrowed star. "He's going to make a great father."
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