Jerry Koosman -- who played on the 1969 "Miracle" Mets team that won the World Series -- has died ... the team announced.

Koosman passed away surrounded by family in Osceola, Wisconsin ... the Mets shared on the team's Medium account.

According to the team ... Jerry had battled multiple illnesses before his death.

The pitcher won Game 2 of the '69 World Series ... before topping it off with the Game 5 W that clinched the series for the team.

Jerry's teammate Ron Swoboda spoke out about his death ... "Jerry was our protector. Any time the opposition threw at our guys, Jerry took care of it."

In addition to his '69 World Series title ... Jerry also boasted 2 All-Star appearances.

Jerry was 83.

RIP