BOSTON — Patriots tight end Rob Gronkowski says he is retiring from the NFL after nine seasons.

Gronkowski announced his decision via a post on Instagram on Sunday, saying that a few months shy of his 30th birthday, “it’s time to move forward and move forward with a big smile.”

“It all started at 20 years old on stage at the NFL draft when my dream came true, and now here I am about to turn 30 in a few months with a decision I feel is the biggest of my life so far,” Gronkowski wrote in his post. “I will be retiring from the game of football today.”

Gronkowski’s agent, Drew Rosenhaus, confirmed his client’s decision to retire.

The tight end, who turns 30 in May, leaves as a three-time Super Bowl champion who has established himself as one of the most dominant players at his position.

But he has been dogged in recent seasons by back, knee, ankle and arm injuries that have limited his ability to stay on the field.

It led him to hint at retirement following New England’s Super Bowl loss to the Eagles to end the 2017 season and again last month after the Patriots’ Super Bowl win over the Rams.

In his Instagram post, Gronkowski thanked the Patriots organization and its fans for their support during his nine NFL seasons.

“Thank you for everyone accepting who I am and the dedication I have put into my work to be the best player I could be,” Gronkowski wrote.

Gronkowski was one of Patriots quarterback Tom Brady’s favorite targets since being drafted in the second round of the 2010 draft.

He had his fourth career 1,000-yard receiving season in 2017 and was an All-Pro for the third time that season.

But at times he looked like a shell of himself during the Patriots’ Super Bowl run this past season. Gronkowski finished the 2018 regular season with just 47 catches for 682 yards and three touchdowns.

He had one of his best games of the season in the Patriots’ Super Bowl win over the Rams, hauling in six catches for 87 yards, including two receptions on New England’s only touchdown drive during their 13-3 victory.

A fan favorite in New England for his gregarious and playful persona that included awkward dance moves and touchdown celebrations, Gronkowski was one of the most dominant tight ends of his era.

His 12 career postseason touchdown receptions are the most by a tight end in NFL playoff history. His 81 career postseason catches are also best among tight ends.

He’ll also retire with 79 career TD catches — regular season and playoffs — which is third all-time by a tight end behind only Antonio Gates (116) and Tony Gonzalez (111).

Brady and Gronkowski connected on 78 TD passes. It is the second-most scoring connections between a quarterback and a tight end in NFL history behind only Philip Rivers and Gates (89) and is fifth overall between quarterbacks and all pass-catchers.