A small-time, but naturally gifted boxer is suddenly awarded the opportunity of a lifetime to fight against a famous heavy-weight champion, the outcome of which could change his life forever.
On New Year's Day in 1976, world heavyweight boxing champion Apollo Creed has successfully defended his title in a split decision against challenger Rocky Balboa. He and Rocky are taken to the same hospital. Apollo challenges Rocky to a rematch, but Rocky declines and retires from professional boxing. His girlfriend, Adrian, supports his choice, and so do his doctors, who reveal that he will require surgery for a retinal detachment, a condition that could lead to permanent blindness. In a private moment, Rocky goes to see a recuperating Apollo, and wants a truthful response to his question of whether Apollo gave his all in the fight; Creed confirms that he did. After Rocky is released from the hospital, he enjoys the benefits of his life's changes: Rocky's new fame attracts an agent who sees Rocky as a potential endorsement and sponsorship goldmine, and his sudden wealth encourages him to propose to Adrian. She happily accepts, and they marry in a small ceremony. Soon after, Adrian reveals that she is pregnant.
Three years after winning the heavyweight championship against Apollo Creed, Rocky Balboa has had a string of ten successful title defenses. His fame, wealth, endorsements, and celebrity profile have increased, leading him to participate in an exhibition charity event against the world wrestling champion, Thunderlips (Hulk Hogan).
Ivan Drago, a Soviet boxer, arrives in the United States with his wife, Ludmilla, a Soviet swimmer and a team of trainers from the Soviet Union and Cuba. His manager, Nicolai Koloff, takes every opportunity to promote Drago's athleticism as a hallmark of Soviet superiority. Motivated by patriotism and an innate desire to prove himself, Apollo Creed challenges Drago to an exhibition bout. Rocky has reservations, but agrees to train Apollo despite his misgivings about the match.
Shortly after Rocky Balboa's victory over Ivan Drago in Moscow, he, his wife Adrian Pennino, his brother-in-law Paulie, and his trainer Tony "Duke" Evers, return to the United States, where they are greeted by Rocky's son, Robert. At a press conference, boxing promoter George Washington Duke attempts to goad Rocky into fighting his boxer, Union Cane, who is now the top-rated challenger, but Rocky declines the offer. Washington refuses to give up on the huge payday fight with Balboa and surmises he needs to come up with an angle to convince him to fight.
Rocky Balboa, now in his late fifties and retired from boxing, lives a quiet life as a widower, Adrian Pennino having died from cancer four years prior. He now runs a small but successful Italian restaurant named after her, where he regales his patrons with stories of his past. He also battles personal demons from his grief over Adrian's death, the changing times, and his eroding relationship with his son Robert, a struggling corporate employee. Paulie Pennino, Rocky's brother-in-law, continues to support him whenever he can, and is guilt-ridden over his poor treatment towards his late sister.
In 1998, Adonis Creed, the son of an extramarital lover of former heavyweight champion Apollo Creed, is serving time in a Los Angeles youth detention center when Creed's widow, Mary Anne, visits and offers to take him in.
Three years after his loss to "Pretty" Ricky Conlan, Adonis Creed scores a string of victories, culminating in a victory over Danny "Stuntman" Wheeler to win the WBC World Heavyweight Championship. Now a worldwide star, Adonis proposes to his girlfriend, Bianca Taylor, who agrees to marry him. When Bianca suggests starting a new life together in Los Angeles, Adonis is reluctant to leave his life in Philadelphia behind.
Adonis has been thriving in both his career and family life, but when a childhood friend and former boxing prodigy resurfaces, the face-off is more than just a fight.