Kim confirmed on her website that the baby girl was born on January 15 and weighed in at 7 lbs., 6oz.
"Kanye and I are happy to announce the arrival of our healthy, beautiful baby girl," the reality TV star wrote. "We are incredibly grateful to our surrogate who made our dreams come true with the greatest gift one could give and to our wonderful doctors and nurses for their special care. North and Saint are especially thrilled to welcome their baby sister."
Kim added, "We're so in love."
TMZ confirmed the news back in September that the powerhouse couple would be adding to their family thanks to a surrogate.
Kim had been vocal about wanting a third child but is reportedly unable to give birth again due to medical concerns. She had also been vocal about finding a surrogate.
In July, Us Weekly reported that the couple's surrogate is a San Diego mom in her late 20s whom they found through a surrogate agency.
The couple are already parents to North, 4, and Saint, 2.
This won't be the last addition to the Kardashian clan this year—both Kylie Jenner and Khloé Kardashian are reportedly due in the coming months.
The name Kim Kardashian is synonymous with style. Mom to baby North and wife of recording superstar Kanye West, Kardashian manages to dominate reality TV, the business world and social media with apparent ease. While some celebrities drastically alter their styles after becoming mothers, Kardashian has stayed consistent. Her secret weapon is knowing what works for her and sticking to it — even with a diaper bag in tow.