The tennis ace, 24, and former Home And Away actress, 22, welcomed a baby girl into the world at Sydney's North Shore Private Hospital at 1.45 am local time.
Their publicist ROB AIVATOGLOU says, "At this stage Lleyton and Bec have not announced a name for their new arrival.
"Mother and baby are both doing extremely well. Lleyton and Bec are absolutely thrilled. Most importantly, everything went smoothly and mother and daughter are well."
The sports hero and singer/actress married in Sydney in July (05) after a whirlwind nine month courtship.