Which actor wrote the screenplay for the original Rocky?

Sylvester Stallone wrote the screenplay for the original Rocky.

Stallone wrote the script in 1975 after watching Muhammad Ali fight Chuck Wepner. Wepner lasted until the 15th round before losing by technical knockout, and the bout helped inspire Stallone’s story about an obscure Philadelphia boxer given an unlikely title opportunity.

The screenplay was reportedly written in about three and a half days. Stallone also insisted on playing Rocky Balboa, rejecting offers that would have allowed the film to be made with a better-known star. United Artists ultimately agreed to cast him, helping launch one of cinema’s most enduring sports franchises.

Robert Chartoff and Irwin Winkler were producers, not the screenplay’s credited writer. John G. Avildsen directed the film. Rocky opened in 1976, became a major success, and won the Academy Award for Best Picture.