Conor McGregor posted the very first pic of his new baby early Sunday morning -- a kid with steely eyes and a tough lookin' jaw. Kid's got a big right arm, too.

He'll clearly destroy all other babies in the maternity ward.

The UFC superstar's girlfriend Dee Devlin looks great -- smiling with the kid at Coombe Maternity Hospital in Ireland, where the baby was born Friday night.

By the way, Conor Jr. is already proving to be a massive hit on social media -- with more than 40,000 followers on Instagram in the first 48 hours of his life.