Roberto Clemente's #21 To Be Worn By All Pittsburgh Pirates For Clemente Day

Unprecedented Roberto Clemente honor coming up for the Pittsburgh Pirates ... team officials say they'll unretire the Hall of Famer's #21 so their players can wear it for Clemente Day next week.

The team says the tribute will go down when the Buccos take on the White Sox on Sept. 9 ... with each Pitt. player set to don Clemente's famous number for the game.

Afterward, Pirates officials say they'll auction off the unis ... with all proceeds going toward the Clemente Foundation and other Pirates charities.

Of course, it's a HUGE honor ... no one in the org. has worn the number for a Pirates game since Clemente tragically died in a plane crash back in 1972. He was only 38.

"Our staff and players are excited to wear the number 21 with pride as we constantly search for ways to not only honor Roberto's legacy but to keep his memory alive through our community actions," Pirates chairman Bob Nutting said.

"We recognize what this moment represents for all of us within the organization, the Clemente Family, our fans, and the people of Puerto Rico. We take great pride in representing such a great ambassador of the game."

The Pirates and MLB as a whole have honored Clemente every September since 2002 with Clemente Day ... with Pittsburgh doing different things every year to carry on RC's legacy.