Rob Gronkowski, the dominant tight end who helped lead the New England Patriots to three Super Bowl titles in nine seasons while cultivating a goofy, frat boy persona off the field, announced his retirement from the N.F.L. on Sunday.

In an Instagram post, Gronkowski, 29, widely considered one of the most talented tight ends to ever play, thanked the team and its fans for drafting his “silliness” back in 2010 and acknowledged the uncertainty of what will come next for him.

“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,” he said. “But now its time to move forward and move forward with a big smile knowing that the New England Patriots Organization, Pats Nation, and all my fans will be truly a big part of my heart for rest of my life.”