Donny Johnson (Michael B. Jordan), an illegitimate son of Apollo Creed who never met his dad (Apollo died before he was born and his mother shortly afterward) is raised in group/foster homes and is quite a troublemaker. Apollo's wife (Phylicia Rashad) eventually takes him in and he spends his teen years living with her in California, going to college and getting a good job with a financial company. Donny (Adonis) does know his heritage and is actually 15-0 fighting in Tijuana.
Donny decides to pursue boxing as his career, quits his job, moves to Philly and asks Rocky Balboa (Sylvester Stallone) to train him. Rocky does, only out of respect for Apollo. Donny and Rocky agree to keep his Apollo background secret as Donny wants to make it on his own. They win a big fight against an undefeated pro; whose manager reveals afterwards that Donny is, in fact, Apollo's son.
Suddenly, the English WBC champ, "Pretty Ricky Conlan (Tony Bellew) who is about to go to jail for seven years, wants his final big payday bout to be against Donny, but only if he goes by the name of CREED. He agrees.
Rocky is diagnosed with Hodgkin's but doesn't want treatment. He's ready to be with Adrian, who died years ago. Donny convinces him to fight the disease. Rocky, even during his own Chemo sessions, puts Donny through the classic Rocky training routine.
The fight takes place in Liverpool with the fans entirely on Conlan's side (See Rocky IV). Adonis looks helpless in the early rounds but eventually it becomes a slugfest. The fight ends with an almost knockout blow by Creed, just as the final bell sounds. The champ staggers and barely stands up before the 10-count. Conlan wins the decision, but Creed wins the crowd and the night.