The Man Who Resurrected Lady Gaga -- Revealed

12/6/2010 7:43 PM PST
The mystery man who donated half-a-million bucks to an AIDS charity and brought Alicia Keys, Lady Gaga and a ton of other celebs back to life (on Twitter)  -- has been revealed ... as a BILLIONAIRE.

TMZ has learned ... pharmaceutical mogul Stewart Rahr donated roughly $500,000 earlier today to the Digital Death campaign  ... which benefits the Keep a Child Alive organization.

Rahr's donation freed up scores of celebs who pledged to go silent on their social media sites until the group raised $1 million.