Gronkowski, 33, announced his retirement Tuesday via social media.
"I want to thank the whole entire first class Buccaneers organization for an amazing ride, trusting me to come back to play and help build a championship team," Gronkowski said in his statement. "I will now be going back into my retirement home, walking away from football again with my head held high knowing I gave it everything I had, good or bad, every time I stepped out on the field.
"The friendships and relationships I have made will last forever, and I appreciate every single one of my teammates and coaches for giving everything they had as well. From retirement, back to football and winning another championship and now back to chilling out, thank you to all."
However, Gronkowski's agent told ESPN's Adam Schefter that he wouldn't be surprised if his client could be coaxed out of retirement for a second time by Buccaneers quarterback Tom Brady.
"It would not surprise me if Tom Brady calls him during the season to come back and Rob answers the call," Drew Rosenhaus told Schefter. "This is just my opinion, but I wouldn't be surprised if Rob comes back during the season or next season."
Gronkowski had previously retired after the 2018 season with the New England Patriots because of injuries. The 2010 second-round draft pick out of Arizona largely credits Brady for setting the expectations for his career, and it was Brady who summoned him out of retirement in 2020 to play for the Bucs.
Though their personalities differed immensely -- Gronkowski playful, fun-loving and never known to have a bad day by coaches or teammates; Brady, methodical and intense -- they developed a close connection, both on and off the field.
"Teammate, friend, brother, just a few of the words that come to mind when I think of @gronk," Brady wrote in an Instagram post. "Nobody has ever embodied the idea of 'leaving it all out on the field' like Rob has throughout his entire career. Every single snap, I knew that no matter how many people you put in front of him, he was going to get to his spot.
"Even more important is the person he was off the field. Focused when he had to be, and FUN the rest of the time. Having Gronk in your locker room was every NFL [player's] dream. I'm proud of all that we've accomplished together, and even more excited for all you have ahead of you. Congrats Gronk, you deserve it."
Gronkowski is the second key member of the Buccaneers' offense to retire this year, following guard Ali Marpet, who retired in February. Brady himself announced his retirement in February only to unretire 40 days later.
Gronkowski's breakthrough year came in 2011, when he set the NFL record for most receiving touchdowns by a tight end with 17. The year before, Gronkowski unveiled what became known as his signature move -- the "Gronk Spike," where he forcefully slammed the ball onto the field after every touchdown he scored.
Gronkowski won four Super Bowls --- three with the Patriots (XLIX, LI, LIII) and one with the Buccaneers (LV) in 2020, a game in which he had two touchdowns, or "tuddies" as he liked to call them.
"Rob is a true professional who left it all on the field for us the past two seasons and helped establish a championship culture in our building," Buccaneers general manager Jason Licht said in a statement. "He played a crucial part in our Super Bowl LV championship season in 2020 and battled through a number of injuries last year while on the way to one of the most productive receiving yardage seasons in his 11-year career. It is always difficult to see a great player walk away from the game when he is still enjoying that kind of success, but the overwhelming emotions I feel today are gratitude and respect for one of the greatest tight ends who ever played the game. While his on-field accomplishments will surely earn him a gold jacket and a place in the Pro Football Hall of Fame, it is his humble attitude and team-first approach to the game that truly defined his career."
Gronkowski was named a first-team All-Pro in 2011, 2014, 2015 and 2017, and was picked to five Pro Bowls (2011, 2012, 2014, 2015 and 2017). He led the NFL in receiving touchdowns in 2011 and was named NFL Comeback Player of the Year in 2014. He was named to the NFL's 2010s All-Decade Team and its 100th Anniversary All-Time Team.
He leaves the game with the most career touchdowns by a tight end in postseason history (15) and the second-most at any position, behind only receiver Jerry Rice (22). He also has the most 100-yard games by a tight end in NFL history and the most total TDs in a single season by a tight end in league history (18 in 2011).
Gronkowski's 92 total career touchdowns are 12th most in NFL history and third most at the tight end position behind Antonio Gates (116) and Tony Gonzalez (111). He was the only tight end in NFL history to post three seasons of 1,000 yards receiving and 10-plus touchdowns (2011, 2014 and 2015).