Jerry Jones Tells Billionaire Pal ... I'M NOT SIGNING MANZIEL

Seems Johnny Manziel has finally lost his biggest fan ... with Jerry Jones telling his billionaire pal, T. Boone Pickens, the Heisman Trophy winner is persona non grata in Dallas.

So, how do we know?

Pickens told us he had dinner with his fellow Texas billionaire buddy the other night and JJ made it clear Manziel is NOT in the Cowboys' future plans.

In fact, Pickens took it one step further ... saying Manziel will NEVER play in the NFL ever again.