The actor's rep confirms to E! News that Duhamel recently popped the question to the Black Eyed Peas singer.
So far, there's no word on a wedding date.
Duhamel, 35, and Fergie, 32 (real name: Stacy Ferguson), have been an item since September 2004. They met when she made a guest appearance on Las Vegas.
The proposal comes after Fergie told Blender earlier this month that she was in no real rush to get engaged because she and Duhamel were "practically married, anyway."
"I'm madly in love with him," she said of her now fiancé. "He understands how to treat a woman and give me respect."
Aside from planning her nuptials, Fergie is working on completing her second solo album, the follow-up to 2006's The Dutchess.
She has also signed on to perform a remix of Michael Jackson's "Beat It" on the upcoming 25th-anniversary edition of Thriller.
Duhamel is currently in his fifth season on Las Vegas. Earlier this year, he starred opposite Shia LaBeouf and Megan Fox in Transformers.
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