A 1984 American martial arts romantic drama film directed by John G. Avildsen and written by Robert Mark Kamen, starring Ralph Macchio, Noriyuki "Pat" Morita and Elisabeth Shue. It is an underdog storey in the mould of a previous success, Avildsen's 1976 film Rocky. It was a commercial success upon release, and garnered favourable critical acclaim, earning Morita an Academy Award nomination for Best Supporting Actor.

Daniel LaRusso (Ralph Macchio), a high school senior, moves with his mother (Randee Heller) from Newark, New Jersey to Reseda, a neighbourhood in the San Fernando Valley region of Los Angeles, California. Their apartment's handyman is an eccentric but kindly and humble Okinawan immigrant named Mr. Miyagi (Noriyuki "Pat" Morita).

Daniel befriends Ali Mills (Elisabeth Shue), an attractive high school cheerleader, at the same time angering her arrogant ex-boyfriend, Johnny Lawrence (William Zabka). Johnny is the best student at the Cobra Kai dojo, where he is taught an unethical, vicious form of martial arts. Daniel knows a little karate from books and a few classes at the YMCA, but Johnny easily defeats him in their first encounter. Thereafter, Johnny and his gang of Cobra Kai students torment Daniel at every opportunity.

When Mr. Miyagi sees the gang giving Daniel a savage beating nearly killing Daniel, he intervenes and single-handedly defeats five attackers with ease. Awed, Daniel asks Mr. Miyagi to be his teacher. Mr. Miyagi refuses, but agrees to go with Daniel to the Cobra Kai dojo in order to resolve the conflict. They meet with the sensei, John Kreese (Martin Kove), an ex-Special Forces Vietnam Veteran who sneers at the concepts of mercy and restraint. Kreese and Mr. Miyagi agree to a match between Johnny and Daniel in two months' time at the "All Valley Karate Tournament," where the Cobra Kai students can fight Daniel on equal terms. Mr. Miyagi also requests that the bullying stop while Daniel trains. Kreese orders his students to leave Daniel alone, but under the condition that if Daniel does not show up for the tournament, the harassment will resume and Miyagi himself will also become a target.

Mr. Miyagi becomes Daniel's teacher and, slowly, a surrogate father figure. He begins Daniel's training by having him perform menial tasks such as waxing cars, sanding a wooden floor, and painting a fence and Mr. Miyagi's house. Each chore is accompanied with specific movements involving clockwise/counter-clockwise and up-and-down hand motions. Daniel fails to see any connexion to his training and these chores and eventually feels frustrated, believing he has learned nothing of karate. When he expresses his frustration, Mr. Miyagi shows how while doing these chores Daniel has been learning defensive blocks through muscle memory.

As Daniel's training continues more overtly, his bond with Mr. Miyagi becomes closer. He learns that Mr. Miyagi lost his wife and son in childbirth at Manzanar internment camp while he was serving overseas with the United States Army during World War II. The loss of his family and Daniel's loss of his father further strengthen the father-son surrogacy. Daniel also discovers that the outwardly peaceful and serene Miyagi received the Medal of honour for valour against German forces in Europe. Through Mr. Miyagi's teaching, Daniel learns not only karate but also important life lessons such as the importance of personal balance, reflected in the belief that martial arts training is as much about training the spirit as the body. Daniel applies the life lessons that Mr. Miyagi has taught him to strengthen his relationship with Ali.

At the tournament, Daniel surprises everyone by reaching the semi-finals. Johnny advances to the finals, scoring three unanswered points against a highly skilled opponent. Kreese instructs Bobby Brown, one of his more compassionate students and the least vicious of Daniel's tormentors, to disable Daniel with an illegal attack to the knee. Bobby reluctantly does so, severely injuring Daniel and getting disqualified in the process. As Daniel writhes in pain on the ground, Bobby profusely apologises before he is pulled away. Daniel is taken to the locker room and checked out, with the physician determining that he cannot continue. Although Mr. Miyagi assures him he has already proven himself, Daniel believes that if he does not continue, his tormentors will have gotten the best of him. He gets Miyagi to use a pain suppression technique to allow him to finish the tournament. As Johnny is about to be declared the winner by default, Daniel hobbles into the ring. The championship final is a seesaw battle, as neither Johnny nor Daniel is able to break through the other's defenses.

Daniel successfully uses a scissor leg technique, tripping Johnny and delivering a blow to the back of the head, giving Johnny a nose bleed. The match is paused for Johnny to be looked at by Kreese. Kreese directs Johnny to sweep Daniel's injured leg, an unethical move. Johnny looks horrified at the order but reluctantly agrees after Kreese's intimidation. Despite the moves, Daniel gets up each time.

Eventually, Daniel and Johnny are tied, with the next point deciding victory. Daniel tries to kick Johnny with his injured leg but Johnny grabs it and delivers illegal contact to Daniel's injured knee. Daniel, barely able to stand, assumes the "Crane" stance, a technique he observed Mr. Miyagi performing on the beach during his training. After the referee signals to begin, Johnny lunges in. Daniel jumps in the air and delivers a front kick to Johnny's chin, winning the tournament.

Johnny, having gained newfound respect for his adversary, takes Daniel's trophy from the Master of Ceremonies and presents it to Daniel himself, sincerely proclaiming "You're all right, LaRusso! Good match!" Mr. Miyagi, Ali, and Daniel's mother look on admiringly as Daniel celebrates his victory.