He played 90 percent of the team's defensive snaps in Super Bowl LII and was arguably their most effective player on the front seven.
"I've missed way too much for way too long.and I'm done", Harrison wrote on his Instagram account.
Harrison had 84.5 sacks, 34 forced fumbles, 26 passes defensed, nine fumble recoveries, eight interceptions and a touchdown in 193 career appearances.
Harrison, who made a brief retirement in 2014 before rejoining the Steelers weeks later, finished with 793 tackles, including 84.5 quarterback sacks, in 193 National Football League games.
Father Time appeared to finally get the better of Harrison in 2017, though. Harrison lashed out at commissioner Roger Goodell, calling him "a crook" in a 2011 magazine article. He signed a deal with Cincinnati in the spring of 2013 but played only sparingly, leading him to retire in the fall of 2014.