Louis Pasteur is an unseen vampire on the HBO original series True Blood. A famous French chemist who is remembered for his remarkable breakthroughs in the causes and prevention of diseases, Louis contributed toward the invention of Tru Blood and was mentioned on the episode "You Smell Like Dinner", in the series' fourth season.
He is mentioned to Bill Compton by Nan Flanagan in 1982. In London, England when she sees Bill (not kill his food), she talks about the Vampire Authority and says that Louis Pasteur is a vampire who is working on an alternate substance for vampires. ("You Smell Like Dinner")