Nine years after he played his last game, Bernie Williams officially will retire Friday at Yankee Stadium.

Williams, whose last season was 2006, will sign retirement papers before the Yankees host the Mets in the first of three Subway Series games. Williams will then throw out the ceremonial first pitch.

Also Friday, the Yankees will unveil a logo related to the retirement of Williams’ No. 51 — which will happen May 24.

In 16 years with the Yankees, Williams won four World Series, was an All-Star five times and won four Gold Gloves.

“He has been busy with is music the whole time,’’ Girardi said of the gap between Williams’ final game and signing retirement papers, which are nothing more than a formality.