Louis Tomlinson: I Just Had the FIRST 1D Baby!

There's a new generation of One Direction ... Louis Tomlinson and his former GF have a baby boy.

Briana Jungwirth gave birth this week in L.A. It's the first child for both of them -- Louis is 24 and Briana's 23 -- and the first kid for any of the 1Ders. No word on a name yet.

It's unclear if Louis was in town for the birth. He and Briana only dated briefly before she got pregnant, but we're told they've gotten much closer during the pregnancy ... especially after Louis made a special trip to L.A. to hang with her family over the summer.

Mazel tov!