The Grammy-winning singer, 33, and her husband since 2010, Kasseem Dean, aka Swizz Beatz, welcomed a baby boy, Genesis Ali Dean.
She posted an image on her Instagram account, saying the baby was born Saturday at 1:52 a.m., and was 6 pounds, 5 ounces.
"The joy of joy is joy!! It's a boy!!" she wrote.
Keys and Beatz are also parents of 3-year-old son Egypt. In addition, Beatz, 35, has three more children from previous relationships.
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Keys announced the news that she was expecting her second child on her Instagram account, with a photo of her and her husband both wearing white and embracing her baby bump.
"Happy Anniversary to the love of my life @therealswizzz !! And to make it even sweeter we've been blessed with another angel on the way!!" she revealed.
Keys continued to gush, "You make me happier than I have ever known! Here's to many many more years of the best parts of life!"