Yeah, you've heard the story before ... because Harrison has retired before -- but this time, Deebo says he meant it.

"I've missed way too much for way too long...and I'm done," the 39-year-old Pittsburgh Steelers legend announced on social media.

He also posted several photos of his kids -- suggesting he's ready to become a full-time dad.

"Many thanks to my family, coaches, the fans, and everyone who played a role in my football life. #2ndAndFinalRetirement #HarrisonFamilyValues #BlessedAndHighlyFavored #GodsPlan."

Harrison was a monster in the NFL -- 5 Pro Bowls, 2 Super Bowl rings and he was the NFL Defensive Player of the Year in 2008.

Besides the Steelers, he also played for the Bengals and most recently the New England Patriots.