Harrison announced his retirement on Monday, saying in an Instagram post: "I've missed way too much for way too long and I'm done".
Harrison came into the league as an undrafted free agent in 2002. He was a Pro Bowler for five straight seasons from 2007-2011, a First-Team All-Pro selection in 2008 and 2010, and the NFL Defensive Player of the Year in 2008.
Harrison had 84.5 sacks, 34 forced fumbles, 26 passes defensed, nine fumble recoveries, eight interceptions and a touchdown in 193 career appearances.
He then spent some time with the Baltimore Ravens and the NFL Europe's Rhein Fire before ending up back with the Steelers in 2004. Pittsburgh cut him on December 23, 2017, after he had played in only five games and been a health scratch much of the season.
The long-time National Football League player had previously announced his retirement in 2014 following a one-year stint with the Cincinnati Bengals, but returned to the game with the Steelers for the next season.
Following his release from the Steelers, Harrison signed with the Patriots and played one regular season game and all three playoff games for them.
After a one-year stint with the Cincinnati Bengals, Harrison returned to Pittsburgh in August 2014 and announced in September that he would retire as a Steeler.