The couple announced the birth of their first child on social media Sunday. Their daughter was born Thursday.
"She's here! Luna Simone Stephens, we are so in love with you! And sleepy. Very sleepy," Teigen wrote on Instagram, posting a photo of a sign announcing the baby's weight of 6lb 11oz.
Legend also took to Twitter to share his joy, posting: "Our new love is here! Luna Simone Stephens, born on Thursday, the 14th. We couldn't be happier!"
The 37-year-old R&B star and the 30-year-old model were married in 2013.
The couple announced the pregnancy in October after Teigen opened up about their fertility struggle and how she had undergone IVF treatments.