The rapper -- who just revealed her pregnancy last month amid divorce proceedings with long-time partner Offset -- confirmed the news Thursday with pics and videos of her holding the baby girl in the hospital bed.

Offset's with Cardi in the hospital in the photos ... sitting with their kids, and each holding on to the newest addition to the family -- who Cardi calls "the prettiest lil thing." She writes 9/7/24 in the caption -- so, looks like the baby was born Saturday.

Cardi shared pics of herself breastfeeding, holding the baby and smiling big -- with the post-baby glow still lighting up her face.

As you know ... Cardi announced she was having the third kiddo just a day after filing for divorce from Offset -- with sources telling us there was no cheating involved in their split, and the two basically just drifted apart.

Her divorce docs did confirm Offset's the father of her child BTW ... and, she's asking for child support to help pay for the child's expenses.

Despite the split, we know the two have a strong co-parenting relationship ... recently linking up for their son Wave's 3rd birthday party earlier this month.

She danced with baby Wave in her arms and took pics alongside Offset, their shared children and his kids from previous relationships ... a very amicable scene, especially when compared to other celeb splits.

That said, we're told the two aren't getting back together ... just working as a team to raise their kiddos.