Friday the 13th is an American horror media franchise that comprises twelve slasher films, a television series, novels, comic books, video games, and tie‑in merchandise. The franchise primarily focuses on the fictional character Jason Voorhees, who was thought to have drowned as a boy at Camp Crystal Lake due to the negligence of the camp staff. Decades later, the lake is rumored to be "cursed" and is the setting for a series of mass murders. Jason is featured in all of the films, as either the killer or the motivation for the killings. The original film was written by Victor Miller, produced and directed by Sean S. Cunningham, and released by Paramount Pictures. The films have grossed over $468 million at the box office.

Although the films were not popular with critics, Friday the 13th is considered one of the most successful media franchises in America—not only for the success of the films, but also because of the extensive merchandising and repeated references to the series in popular culture. Jason's hockey mask has become one of the most recognizable images in horror and popular culture.

In the original Friday the 13th (1980), Mrs. Pamela Voorhees (Betsy Palmer) stalks and murders the teenagers preparing Camp Crystal Lake for re‑opening. She is determined to ensure the camp does not reopen, after her son Jason (Ari Lehman) drowned in the lake, due to the negligence of two staff members. The last counselor, Alice Hardy (Adrienne King), fends off Mrs. Voorhees long enough to grab a machete and decapitate her. In Friday the 13th Part 2 (1981), Jason (Steve Daskewisz/Warrington Gillette) is revealed to be alive and fully grown. After killing Alice Hardy, Jason returns to Crystal Lake to guard it from all intruders. Five years later, a group of teenagers arrive at Crystal Lake to be trained as camp counselors, but Jason murders them. Ginny Field (Amy Steel), the last counselor Jason attempts to kill, finds a cabin in the woods with a shrine built around the severed head of Mrs. Voorhees. Ginny fights back and slams a machete through Jason's shoulder. Jason is left for dead as Ginny is taken away in an ambulance.

During the events of Friday the 13th Part III (1982), Jason (Richard Brooker) removes the machete from his shoulder and finds his way to Chris Higgins' (Dana Kimmell) local homestead. Chris returns to her property with some teens, and Jason kills anyone who wanders into the barn where he is hiding. Taking a hockey mask from a victim to hide his face, Jason leaves the barn to kill the rest of the group. Chris seemingly kills Jason with an axe to his head, but the night's events drive her into hysteria as the police take her away. Friday the 13th: The Final Chapter (1984) continues where Part III leaves off, with Jason (Ted White) found by the police and taken to the local morgue after removing the axe. Upon arrival, Jason awakens to kill the coroner and a nurse before returning to Crystal Lake. A group of teens rents a house on Crystal Lake and fall victim to Jason's rampage. After killing the teens, Jason seeks out Trish (Kimberly Beck) and Tommy Jarvis (Corey Feldman), who live next door. While distracted by Trish, Jason is attacked and ultimately killed by Tommy.

Friday the 13th: A New Beginning (1985) follows Tommy Jarvis (John Shepherd), who was committed to a mental health institution after the events of The Final Chapter and grew up constantly afraid that Jason (Tom Morga) would return. Roy Burns (Dick Wieand) uses Jason's persona to become a copycat killer at the halfway home to which Tommy has moved. Tommy, supervisor Pam (Melanie Kinnaman), and a young boy named Reggie (Shavar Ross) manage to defeat Roy. They eventually learn that Roy had a son who was murdered by one of the patients at the institution, triggering Roy to take on Jason's likeness and kill everyone there. Friday the 13th Part VI: Jason Lives (1986) begins with Tommy (Thom Mathews) visiting Jason's grave after being released from another mental institution. Tommy inadvertently resurrects Jason (C. J. Graham) with a piece of the fence surrounding the cemetery acting as a lightning rod. Jason immediately heads back to Crystal Lake and kills the people working at the new summer camp. Tommy eventually chains Jason to a boulder that he tosses into the lake, where he leaves Jason who is revealed to be alive.

Friday the 13th Part VII: The New Blood (1988) begins an indeterminate length of time after Jason Lives. Jason (Kane Hodder) is resurrected again by the telekinetic Tina Shepard (Lar Park Lincoln), who is trying to resurrect her father whom Tina caused to drown in the lake when she was a child. Jason once again kills those who occupy Crystal Lake and is returned to the bottom of the lake after a battle with Tina. Jason is resurrected again in Friday the 13th Part VIII: Jason Takes Manhattan (1989) by an underwater electrical cable. He follows a group of students on their senior class cruise to Manhattan, where he kills the ship's crew and the majority of the students. Upon reaching Manhattan, Jason chases Rennie (Jensen Daggett) and Sean (Scott Reeves), the two remaining students, into the sewers. Jason eventually melts away when the sewer is flooded with toxic waste.

In Jason Goes to Hell: The Final Friday (1993), Jason, through an unexplained resurrection, is hunted by the FBI at Crystal Lake. The FBI sets up a sting that successfully kills Jason. Through possession, Jason manages to survive by passing his black heart from one being to the next. It is revealed that he has a sister and a niece, and that he needs them to get his body back. Jason resurrects himself, but his niece, Jessica Kimble (Kari Keegan), stabs him with a mystical dagger and he is dragged into Hell. Jason X (2001) takes place in the future, when Jason has again been inexplicably resurrected. A scientist, Rowan LaFontaine (Lexa Doig), decides that cryonic suspension is the only method of stopping him, but Jason breaks free and kills the army personnel guarding him before he can be again imprisoned. Rowan manages to lure Jason into the cryo‑chamber, but he ruptures the tank and freezes both himself and Rowan. Over 400 years later, a team of students studying Earth discover Jason's body and take it into space. Upon being thawed by the team, he proceeds to murder everyone aboard the spacecraft. He is seemingly killed, but is then resurrected via nanotechnology as a cyborg version of himself. Finally, he is ejected into space and incinerated by Earth Two's atmosphere, his mask falling to the bottom of a lake.

The next Friday the 13th film, Freddy vs. Jason (2003), was a crossover with A Nightmare on Elm Street. Set in the contemporary period, Freddy Krueger (Robert Englund) resurrects Jason (Ken Kirzinger) and sends him to Springwood hoping that he will create enough fear among the residents that Freddy will be strong enough to invade their dreams. Jason accomplishes this but refuses to stop killing. A battle ensues both in the dream-world and at Crystal Lake. The outcome is left ambiguous, as Jason surfaces from the lake holding Freddy's severed head, which winks and laughs.