A representative for Keys said she gave birth Thursday night in New York.
The couple have named their son Egypt Dean.
It's the first child for the 29-year-old superstar and the fourth child for Beatz, whose real name is Kaseem Dean.
The couple was married July 31.
Swizz Beatz, 31, took time to tweet on Friday: "I'm so thankful for everything I been blessed with in my life."
Singer Mary J. Blige also tweeted her congratulations on the birth.