The singer and her fiance, Matthew Rutler, welcomed their first child together -- Summer Rain Rutler, ABC News has confirmed.
"So proud to welcome our beautiful daughter Summer Rain Rutler into the world," Aguilera wrote on Twitter.
Aguilera, 33, and Rutler announced earlier this year that they were engaged and expecting. In March, she revealed that they were going to have a baby girl.
This is the second child for Aguilera, currently a judge on "The Voice." Her son, Max, from a previous marriage, is 6.