The 32-year-old yoga instructor took to Instagram to share the wonderful news.
“We are so pleased to introduce you to our new baby, Leonardo Ángel Charles Baldwin. It was such a special day bringing him into this world,” Hilaria penned alongside a beautiful photo of her cradling her newborn in her arms.
Moments later, 58-year-old Alec re-posted the same snap on his Instagram page.
Leonardo was born in New York City on Monday.
The couple, who married in 2012, are already the proud parents to three-year-old daughter Carmen and one-year-old son Rafael.
The 30 Rock star announced they were expecting their third child together back in March with a loved up post of him and Hilaria sharing a tender kiss on the streets of New York, as the pregnant beauty held a blue teddy bear between them.
“Ireland, Carmen, Rafael, Hilaria and I are excited to share with you that we are going to have another little addition to our family. Another little boy coming this Fall,” he lovingly penned.
Alec shares 20-year-old daughter Ireland Baldwin with his ex-wife Kim Basigner.
Hilaria has garnered a cult following on Instagram thanks to her daily yoga posts.

What a beautiful announcement!
Since welcoming her children into the world, Hilaria has even started to incorporate them into her routines.
“I wanted to do a pose each day. I’ve now realised that it’s really hard to think up a new one every day! But I made a promise and I’m going to keep it. The best poses are the more spontaneous ones,” she explained to Hello! Magazine.
Congrats to Alec and Hilaria on their newest addition!