TMZ Sports has learned ... Triple C and his fiancée, Ana Karolina, are expecting their first child together -- a baby girl due in November.

Of course, Cejudo and Karolina first went public back in November 2020 ... and have been inseparable ever since.

Fun fact -- Cejudo previously said Ana was his crush for 4 YEARS before he finally got a chance to meet her through a mutual friend.

Now, the couple is set to welcome their baby girl in just a few months ... and have already decided on a name -- America.

We're told despite announcing their engagement on Instagram on Tuesday, 34-year-old Cejudo actually bent the knee in front of Ana's family in Sao Paulo back on April 29 ... and of course, she said "yes!"

The couple hosted a gender reveal party to share the big news with all their family and friends ... celebrating with some music and pink decorations.

Cejudo -- barring a UFC comeback (which he's flirted with) -- will have PLENTY of time to help with the baby prep ... he announced his retirement from MMA in May 2020 after beating Dominick Cruz at UFC 249.