Coulda been fun ... but Tyron Woodley says the potential fight with Nate Diaz at UFC 219 is officially dead.

"Nate Diaz is obviously scared, homie," Tyron said on the "The Hollywood Beatdown" show (subscribe on the TMZ Sports YouTube page).

Woodley previously said the UFC offered him the fight and he accepted -- and it was up to Nate to sign on the dotted line. But it didn't happen.

Woodley says Nate was asking for WAYYYYYY too much cash -- $15 mil -- and he ain't a $15 million fighter.