Now the main question is: what is the baby girl's name?
If Kylie and Travis are engaged - it's still speculation at this stage - we have a feeling they'll keep it under wraps for as long as possible, in the same style as her pregnancy.
And there's a pretty good reason why fans are blowing up Twitter with their theories.
'Butterflies are just part of the secrets of Kylie, ' Jenner explains.
"Congrats to @kyliejenner & @travisscott for your little miracle", he wrote on an Instagram post. Her new fragrance line, Kimoji Hearts, sold out recently, with the star saving a lot of money by using social media for the whole advertising campaign.
The rapper - real name Jacques Webster - was pictured leaving his girlfriend's home in Calabasas on Monday, where he is believed to have been staying since the birth of their daughter.
Kylie announced her happy news on Instagram and apologies to her fans for keeping them in the dark.
And butterflies in the nursery. "She has a baby name". Mariposa is Spanish for butterfly.
Hopefully we see a Caitlyn-Kris reunion on Keeping Up with the Kardashians soon because if anyone can do it, it's got to be Kylie Jenner's offspring.
Read into that what you will but for now Jenner is celebrating the birth of her daughter's daughter with a heartfelt tribute to the arrival. This is Kylie's moment, to do Kylie's thing, and Kim just showed up with the baby. It's fantastic to be by your side through this journey.
She said pregnancy had been the most "beautiful, empowering and life changing experience" of her life and she is "actually going to miss it". However, the Lip Kit creator waited until after she gave birth to confirm the news.
HollywoodLifers, do you think Kylie and Travis will make it work?