-On Nov. 25, 1975, Rocky Balboa(Sylvester Stallone) is introduced as a small time boxer and collector for Anthony Gazzo(Joe Spinell), a loan shark, living in the Kensington neighborhood of Philadelphia. The World Heavyweight Championship bout is scheduled for New Year's Day, 1976, the year of the United States Bicentennial. When the opponet of undefeated champ Apollo Creed(Carl Weathers) is injured, Creed comes up with the idea of giving a local underdog a shot at the title. Because he likes Rocky's nickname, "The Italian Stallion", he selects the relatively unknown fighter. He puts it in lights saying Apollo Creed meets 'The Italian Stallion'. The fight promoter says the decision is American, but Creed says it is smart.
-To prepare, Rocky trains with a 1920s era gym owner named Mickey Goldmill(Burgess Meredith), who always considered Rocky's fighting potential to be better than his effort, and they conflict over Mickey's motives for the fight. Rocky's friend Paulie(Burt Young), a meat packing plant worker, lets him practice his punches on the meat hanging in the freezer. During training, Rocky dates Paulie's shy, quiet sister Adrian(Talia Shire) who works as a clerk in a local pet store. The night before the fight, Rock confides in Adrian that he does not expect to beat Creed and that he just wants to go the distance with Creed, meaning that lasting 15 rounds meant he was not just another bum from the neighborhood.
-On New Year's Day, the boxing match begins. Apollo Creed does not initially take the fight seriously, and Rocky knocks him down in the 1st round. embarrassing Creed. The fight lasts 15 rounds and both suffer injuries. Rocky suffers his first broken nose and Creed sustains blows to his ribs. Rocky calls out for Adrian, who runs down to the ring. The referee declares a tie and Rocky and Adrian embrace each other.
- Sylvester Stallone as Rocky Balboa, an enforcer for a loan shark by day and a semi-pro boxer by night. He is given the chance at the heavyweight title.
- Talia Shire as Adrian Pennino, Rocky's love interest; a quiet pet store clerk who falls in love with Rocky and supports him through his training.
- Burt Young as Paulie Pennino, Adrian's brother; a meat-packing plant worker by trade, Paulie permits Rocky to train in the freezer.
- Carl Weathers as Apollo Creed, Rocky's opponent and heavyweight champion. The character was influenced by the outspoken, real-life boxing great Muhammad Ali.
- Burgess Meredith as Mickey Goldmill: Rocky's manager and trainer, a former bantamweight fighter from the 1920s and the owner of the local boxing gym.
- Thayer David as George Jergens: the fight promoter who has "promoted fights all over the world".
- Joe Spinnell as Tony Gazzo, loan shark and Rocky's employer
- Cameo appearances
Boxer Joe Frazier has a cameo appearance in the film. The character of Apollo Creed was influenced by outspoken boxer Muhammad Ali who fought Frazier three times. During the Academy Awards ceremony, Ali and Stallone staged a brief comic confrontation to show Ali was not offended by the film. Some of the plot's most memorable moments—Rocky's carcass-punching scenes and Rocky running up the steps of the Philadelphia Museum of Art, as part of his training regime—are taken from the real-life exploits of Joe Frazier, for which he received no credit.
Due to the film's low budget, members of Stallone's family played minor roles. His father rings the bell to signal the start and end of a round, his brother Frank plays a street corner singer, and his first wife, Sasha, was set photographer. Other cameos include Los Angeles televisionsportscaster Stu Nahan playing himself, alongside radio and TV broadcaster Bill Baldwin and Lloyd Kaufman, founder of the independent film companyTroma, appearing as a drunk. Longtime Detroit Channel 7 Action Newsanchor Diana Lewis has a small scene as a TV news reporter. Tony Burtonappeared as Apollo Creed's trainer, Tony "Duke" Evers, a role he would reprise in the entire Rocky series, though he is not given an official name until Rocky II.