Floyd Mayweather Jr. -- New Million Dollar Watch ... NOTHING BUT DIAMONDS!!

If Floyd Mayweather Jr. doesn't knock you out, his new watch -- DRIPPING IN 60 CARATS of flawless diamonds -- will do the job ... and TMZ Sports has the first pics of Floyd with his prized possession.

A source with direct knowledge of the deal tells us Floyd dropped $1 million to have the icy timepiece custom made from Russian cut diamonds.

We're told the Money Team leader flew to NYC this week to check out the watch which was crafted by Rafaello and Co. and was thrilled with the result -- pretty obvious from the look on his face.

The only parts of the watch NOT made of diamonds -- the white gold hands and the leather band.

The most baller part might be the exclusivity. We're told Floyd owns the trademark on the design ... meaning it can't be duplicated without his permission.