A baseball autographed by Pope Francis is being auctioned off to the highest bidder in the wake of his death … and it could end up selling for over five figures.

The late pontiff signed a baseball several years ago … scribbling “Francisco” in black felt-tip pen on a Rawlings MLB ball … and now that he’s dead, the souvenir is hitting the open market.

The baseball is going up for sale through RR Auction … where it’s expected to fetch at least $15,000.

Randy’s been collecting signed Major League baseballs from world leaders and heads of state since 1996, starting with Bill Clinton … and he says he has more than 450 signed balls in his collection.

The auction house tells us the winning bidder will also take home Kaplan’s correspondence with Vatican officials regarding his efforts to get Francis and Benedict XVI to sign.

One of the letters is from Cardinal Peter K. A. Turkson and it reads, in part: “Regretfully, I opened the boxes with the baseballs before reading your message. Not knowing they were from you, I signed them before reading your letter with instructions to have the Popes sign the two baseballs. Sorry about the oversight, if you have other baseballs, kindly send them.”

Francis died Monday from a stroke and heart failure at age 88.