Final Fantasy VII
Aerith Gainsborough is first introduced as a flower seller, when she briefly converses with Cloud Strife, a mercenary working for the anti-government group AVALANCHE, who are fleeing from the bombing of a Mako reactor. The two later meet in Aerith's church in the Sector 5 slums, where she is faced with the possibility of capture by the Turks. Aerith asks Cloud to be her bodyguard for the cost of one date. She is eventually apprehended, but is ultimately rescued by Cloud and his allies. Aerith then joins them in the pursuit of Sephiroth, while also embarking on her own journey of self-discovery.
After a failed attempt to foil Sephiroth's theft of the Black Materia, Aerith ventures alone into the Forgotten City. Cloud and his companions give chase, eventually finding her praying at an altar. As Aerith looks up to smile at Cloud, Sephiroth appears and kills her by impaling her through the torso. Cloud carries Aerith's body out into a lake in the Forgotten City, and releases her back to the Planet. Reeve Tuesti, the head of Shinra Urban and Development, brings the news of her death to Elmyra Gainsborough, Aerith's adoptive mother. The party later learns the reason for Aerith being in the Forgotten City; through her White Materia, Aerith was able to summon Holy, the only force capable of repelling the ultimate destructive magic, Meteor, which has been summoned by Sephiroth. Although Aerith successfully cast Holy before her death, it is held back by the power of Sephiroth's will. When Sephiroth is finally defeated and Holy is released, it appears that it is too late to function as effectively as it should, as Meteor has already come too near to the Planet's surface. While Holy clashes with Meteor, attempting to prevent its impact, the gravity of both Meteor and the Planet pulling on Holy in opposite directions weakens it. Aerith is seen praying with both hands interlocked whilst urging the lifestream to ultimately defend the planet.  The Planet's Lifestream then flows forth, intervening between Holy and Meteor, and acting as a battering ram while aiding in the destruction of Meteor.
Compilation of Final Fantasy VII
In Before Crisis: Final Fantasy VII, set several years prior to the events of Final Fantasy VII, Aerith becomes the target of the original incarnation of AVALANCHE, led by Elfé, who seek to prevent Shinra from acquiring the last surviving Cetra. Instead, AVALANCHE intend to use her to learn the whereabouts of the Promised Land for their own purposes, although a member of the Turks tries to protect her.
Aerith makes several appearances in the CGI film Final Fantasy VII: Advent Children, as Cloud's spiritual guide, urging him to move on with his life and to forgive himself for the tragedies that were beyond his control, telling him that she never blamed him for her death. During their spiritual reunion, Aerith speaks to Cloud in an open meadow laden with flowers, cheerfully and kindheartedly poking fun at how he needlessly burdens himself with the past. However, she acknowledges his suffering and offers kind words of support. One of Aerith's interactions with Cloud comes when each member of the original game's party helps in Cloud's final attack against Bahamut SIN; she appears as the last party member to assist Cloud. She appears again in the final scene of the movie, along with Zack Fair, where she gives Cloud more words of encouragement before she and Zack walk into the light. Near the end of the film, it is discovered that water mixed with the Lifestream flows beneath the flowerbed in Aerith's church, which manifests itself as a cure for Geostigma.
The On the Way to a Smile novella "Case of the Lifestream – Black & White" focuses on Aerith and Sephiroth's respective journeys through the Lifestream after the end of the game but before the events of the film. The "Black" section deals with Sephiroth, the "White" section with Aerith.
Aerith appears in the prequel game Crisis Core: Final Fantasy VII. At the age of 16, she meets Zack, for whom she develops feelings during his stay in Midgar. Aerith and Zack develop a romantic relationship, but Zack is killed at the end of Crisis Core after being held in a Mako chamber for four years in the Shinra Mansion basement. During those years, Aerith helped her adopted mother earn a living by growing and selling flowers, a job that results in her meeting Cloud at the beginning of Final Fantasy VII.
Aerith's character has appeared in several games outside of the Final Fantasy VII continuity. In Final Fantasy Tactics, she appears as a flower girl; when a group of criminals harasses her, Cloud appears and the player engages in battle with the group, letting her escape. Itadaki Street Special features a playable version of Aerith, as well as other Final Fantasy VII characters Tifa Lockhart, Cloud Strife, and Sephiroth. She also appears in Itadaki Street Portable with the same characters from Special, with the addition of Yuffie Kisaragi. While not playable, Aerith appears in the fighting game Dissidia 012 Final Fantasy as an assistant character. She is also featured in the rhythm game Theatrhythm Final Fantasy as a sub-character representing Final Fantasy VII. In LittleBigPlanet 2, Aerith is featured as a downloadable character model.
Aerith makes an appearance in the Kingdom Hearts series as a member of a group dedicated to defeating the Heartless; the group also includes other Final Fantasy VII characters and Leon of Final Fantasy VIII. In the plot of Kingdom Hearts, Aerith suggests a method for defeating the Heartless to protagonists Donald Duck, Goofy and Sora, and gives advice to the player throughout the game. She also appears in Kingdom Hearts: Chain of Memories as a perceptive figment of Sora's memories. Aerith returns in Kingdom Hearts II, wearing a modified version of her dress from Before Crisis. She, Leon and Yuffie run a restoration committee for the town of Hollow Bastion.
Hoshi o Meguru Otome (Maiden who Travels the Planet), a novel written by Benny Matsuyama which appears in the Final Fantasy VII Ultimania Ω guide, follows Aerith's journey through the Lifestream immediately after her death in Final Fantasy VII. Aerith is mentioned in a graffiti in the subway station early in the animated film Wreck-It Ralph; the graffiti reads "Aerith Lives".