A lifelong Yankees fan is suing the team after it lost a letter he received more than 40 years ago from slugger Mickey Mantle, court records say.

Retired cop Michael Kovalovsky noticed a hitch in Mantle’s swing, and sent him a note when The Mick was slumping in 1959.

Kovalovsky, 78, said he loaned the letter to the team along with other memorabilia for use at a museum at the new Stadium, but he never got them back.

The Yankees said the suit is “without merit.”