There was no immediate word on the gender of the babies or their names.
The superstar singer and her mogul husband, who married in 2008, are also parents to a five-year-old daughter, Blue Ivy.
Queen Bey announced her pregnancy in February on Instagram.
"We would like to share our love and happiness. We have been blessed two times over. We are incredibly grateful that our family will be growing by two, and we thank you for your well wishes. The Carters, " she posted.
Father, fans tweet support
Well wishers have been flooding social media since Saturday night.
Beyoncé's father, Mathew Knowles, tweeted, "They're here! #beyonce #twins #jayz #happybirthday" with a photo of balloons that said, "Happy Birthday to the twins! Love, Granddad."
Speculation about the twins' birth had grown in recent days after a woman was photographed entering a Los Angeles hospital on Friday holding a card that read "B + J".
Beyonce is the most-nominated star in the history of the Grammy awards, and her album Lemonade was the world's best-selling record of 2016.
She had been due to headline the Coachella music festival in California in April, but pulled out on her doctor's advice.
The twins' birth - if confirmed - comes only days after actor George Clooney and his wife Amal welcomed their own set of twins, Ella and Alexander.