Tom Hanks gave a GREAT speech at Michael Clarke Duncan's funeral ... retelling a story M.C.D. had told him about why the enormous actor joined (and then unjoined) a Chicago street gang when he was a kid.
Hanks -- who co-starred with Duncan in "The Green Mile" -- had the crowd roaring with laughter ... a touching tribute to his old friend.
As we previously reported, the private ceremony took place at Forest Lawn in Hollywood -- with tons of Duncan's famous friends in attendance ... including Jay Leno, Vivica A. Fox and Holly Robinson Peete.