Romero died "peacefully" while sleeping after a "brief but aggressive battle with lung cancer", his manager, Chris Roe, said in a statement.
"Night of the Living Dead" is the film that made Romero a household name. It made $30 million on a budget of $114,000 and spawned five sequels, including 1978's mall-set Dawn of the Dead, which is widely considered to be one of the best horror movies of all time.
Other films directed by Romero included Creepshow, Monkey Shines and Two Evil Eyes. At the time of his passing he was with his wife Suzanne Desrocher Romero and daughter Tina Romero.
Romero will leave a lasting legacy in cinema, and will still continue to influence filmmakers.
Apart from terrorizing his audience with the flesh-eating ghouls, Romero sent across a social commentary through his zombie movies.More news: The Houston Rockets Are for Sale
Romero told Associated Press: 'People say, "You're trapped in this genre". Night of the Living Dead is often regarded as a criticism of capitalism.
Born in the Bronx, New York, Romero moved to Pittsburgh to attend Carnegie Mellon University. Romero wrote, directed, edited, shot, and acted in the film. "I sympathise with them".
"I always used the zombie as a character for satire or a political criticism, and I find that missing in what's happening now".
Steven King, whose novel The Dark Half was adapted by Mr Romero, called him his "favourite collaborator", adding "there will never be another like you".
Other tributes came from "Halloween" director John Carpenter and horror author Stephen King.
The original is credited as creating now universal rules for zombie films, that the undead lurch slowly and prosper through biting humans who then return as zombies.