Bill Belichick's digital footprint is getting bigger -- the University of North Carolina head football coach just launched his own X account!!

The 72-year-old Tar Heels manager fired off his first post on Elon Musk's platform on Monday ... saying, "'Beat Dook' my first words as a boy are my first words on X! Go Heels!!" while adding in a few hashtags, including #ChapelBill, for good measure.

Coach made sure to prove it's really a legit account and not fake ... taking a break from his first day of recruiting alongside his son, Steve, to hop on "The Pat McAfee Show" to make the big announcement.

It's an important step for Coach -- after all, he's gonna have to interact with a ton of young talent to make sure he builds a competitive roster ... and high schoolers live on social media.

BB only follows 16 users at the moment -- so far, it's a bunch of Tar Heel-related accounts, NFL insiders, his girlfriend and Class of 2026 recruits Zavion Griffin-Haynes and Gavin Waddell.

Life on the internet wasn't always Belichick's jam -- after all, he famously said he's "not on SnapFace" or "InstaChat" ... but he's since come around to making an Instagram as well.

Who said ya can't teach an old dog new tricks??