Cincinnati Bengals rookie quarterback Joe Burrow just got himself an amazing welcome-to-the-NFL gift ... a diamond chain of his jersey number!!
TMZ Sports has learned ... the Heisman Trophy winner wanted to do something special after inking his massive, $36 million rookie deal, so he hit up celeb jeweler Leo Frost to whip up the one-of-a-kind piece.
We're told the awesome #9 pendant is made of 18k white gold and VVS diamonds ... sitting on an 18k white gold prong-set Cuban chain with VVS diamonds.
In other words, the rook's got taste!