Ahch-To is an aquatic planet with numerous islands which served as the origin for the Jedi and, among these islands, the Temple island is the location of the first Jedi Temple. Lanai acted as Caretakers to maintain Temple island's ancient structures and provide care for travelers. Porgs are also native creatures of the planet.
It was also home to Jedi Master Luke Skywalker, who went into self-exile seeking the Ahch-To Jedi Temple after most of his new generation of Jedi Knights were killed during the destruction of his Jedi Temple and Ben Solo's fall to the dark side.
Rey travels to the Temple island on Ahch-To to find Luke Skywalker and it is on this planet that he teaches her about the Force. Although Luke initially refuses to train Rey because of his past failures, he later reluctant agrees to do so. As Rey is called by the dark side of the island during her meditation, Luke warns that her power reminds him of young Ben Solo and that he is scared of what it means for her.
During her time in the island, Rey finds out she has a Force bond with Kylo Ren, and the two of them start to comunicate through Force their connection, developing a closer relationship. After being incited by Kylo about her dependence on her parents and inability to let go of the past, Rey decides to explore the dark side of Ahch-To by herself to find answers. She falls into a hole inside a mirror cave where she sees her reflection repeated as many versions of herself. She asks the cave to show her parents, but it shows her own reflection.
Without answers, Rey cries as she tells the events of the mirror cave to Kylo Ren while he tries to comfort her by telling that she is not alone before they reach out to each other and touch hands across the galaxy. Luke walks in and sees Rey and Kylo together, destroys the hut they are in and demands Rey to leave the island. But Rey confronts Luke about his attempt to murder his nephew before leaving to meet Kylo Ren as she now wants to redeem him.
Luke then decides to burn the Tree Library along with the Sacred Jedi texts, but is surprised when Yoda's Force spirit appears and destroys it with Force lightning. Unbeknownst to Luke, Rey had took the sacred Jedi texts from the library before leaving in the Millennium Falcon.
Afterwards, while still on Ahch-To, Luke creates a Force projection to distract his nephew and the First Order during the Battle of Crait, allowing the Resistance members to escape safely. As he sacrificed all his energy to project himself, Luke watches Ahch-To's binary sunset as he becames one with the Force.
One year later, Rey discovers her Palpatine lineage, and starts to be taken by the dark side in moments of fury. After almost killing Kylo Ren during their duel on the ruins of the second Death Star, Rey arrives on Ahch-To aboard Ren's TIE Whisper. Upon landing on the Temple island, she burns the ship, determined to live in exile out of fear of becoming like her grandfather. However, she is convinced by Luke's Force spirit that her heritage does not define her and that she should confront Darth Sidious. Luke gives her Leia's lightsaber and his old X-Wing, which she uses to travel to Exegol.
- Ahch-To Jedi Temple: A Jedi Temple is hidden on the Temple island of Ahch-To; it was the first of many temples built throughout the galaxy, it was established and maintained by the Jedi Order; it is one of the few Jedi Temples that were not destroyed neither by the Galactic Empire in the Jedi Purge nor by the Galactic Civil War. Based on what had been seen in Star Wars: The Force Awakens and Star Wars: The Last Jedi, it looks like the Ahch-To Jedi Temple had been abandoned by the Jedi Order; even before the Clone Wars, the Jedi Purge and the Galactic Civil War began.
- Tree Library: A uneti tree located on the island in which the Jedi Master Luke Skywalker used as a reading chamber. The library contained the Sacred Jedi texts of the Jedi religion.
- Mirror Cave: A mysterious cave full of mirrors located beneath the surface of the Temple island that is a dark side vergence in the Force.