Shin Megami Tensei: Devil Summoner is a role-playing video game developed and published by Atlus. Forming part of the Megami Tensei franchise, it is the first title in the Devil Summoner series. It was first released for the Sega Saturn in December 1995, and received a port to the PlayStation Portable in December 2005. Despite reports of it being planned for localization, neither version has been released outside Japan.

Set in the city of Hirasaki in modern-day Japan, the story follows a college student whose death at the hands of demons forces his soul into the body of Summoner Kyouji Kuzunoha. Now in Kuzunoha's body, the protagonist must investigate the appearance of demons in the town and the activities of Sid Davis, the Dark Summoner responsible for killing the protagonist and Kuzunoha. The gameplay carries over multiple classic elements from the Megami Tensei series, including first-person dungeon navigation, turn-based battles, and negotiation with demons to recruit them into the player's party.

Devil Summoner began development after the positive reception of Shin Megami Tensei If.... Designed from the outset as a spin-off from the main Megami Tensei series, it drew on elements of detective fiction. It was also the series' first appearance on fifth-generation home consoles. Regular Megami Tensei staff were involved with the project, including director Kouji Okada, writer Ryutaro Ito, and character designer Kazuma Kaneko. The music was composed by Toshiko Tasaki and Tsukasa Masuko. Upon its release in Japan, the original version garnered positive reviews from Japanese press and strong sales. It went on to spawn both a television series and multiple sequels.

Shin Megami Tensei: Devil Summoner is a role-playing video game in which the player takes control of a silent protagonist that can be named and whose personality is determined by dialogue choices made in the game. Navigation is split into two types: standard navigation through the game's three-dimensional (3D) dungeons in a first-person view, and navigation around the protagonist's home of Hirasaki City using a 3D overworld map. During dungeon navigation, the player's route is automatically mapped, and the map can be viewed in the menu screen. Non-playable characters (NPCs) are represented in first-person navigation with 2D sprites, and their speech is represented with head-and-shoulder portraits above dialogue boxes. Quests are available at a location called the House of Divination, which the player can choose to accept in exchange for rewards. Various stores are scattered throughout Hirasaki City for buying items, weapons and armor, and healing the player's party and reserves. A key currency in the game is Magnetite, which is used for summoning demons and as currency in some of the stores.

Enemies are confronted on the overworld map and in dungeons through both random encounters and staged battles. Battles are governed by a turn-based system: the player's and enemy's parties each get a turn during which they can perform available actions. The player party is arranged in a three-by-two grid, with their positioning effecting how they can attack enemies: for instance, short-ranged attacks are made less effective if the selected party member is in the back row. The player has access to multiple commands in battle: "Sword", "Gun", "Magic" and "Extra". Items can also be used in battle, and the player can choose to escape from most encounters aside from key boss battles. An "Auto" option is also available, where the entire party is commanded using the game's artificial intelligence. At the end of each successful battle, experience points are distributed among party members depending on the strength of the enemy, and the protagonist is given Ability Points to assign to six different attributes which affect his performance in battle.

Key elements in the game are negotiation with and the fusion and creation of demons. Encountered in battle, demons can be talked with and negotiated into running from the battle, giving money or items, or joining the player's party. If the negotiation fails, the demon will attack. Once a demon is won over, they are given a loyalty meter which is influenced by the player's actions. If the demon is treated well and performs actions in battle it approves of, its loyalty will increase. If the opposite occurs, the demon will begin to disobey the protagonist, then leave. Demons can be fused together at a special location in the game called the Hotel Goumaden, where fusions are supervised by the NPC Dr. Victor. Demon fusion is governed by a comparability system, with more favorable fusions emerging from better demon compatibility. Demons can also be fused with weapons to grant stat boosts, and after a certain point in the game artificial demons called Zomas can be used and strengthened through repeated fusions.

Devil Summoner takes place in Hirasaki, a coastal Japanese city that has seen a recent rise in supernatural activity. The player character, an unnamed college student, is asked to accompany his girlfriend Kumiko Hatano to check out a book on the occult for her studies. Going to an amusement park to buy some concert tickets at Kumiko's request, the protagonist is attacked by demons and saved by Kyouji Kuzunoha, a Summoner belonging to an ancient clan dedicated to protecting Japan from supernatural threats. Shortly after leaving him, Kuzunoha dies under mysterious circumstances. Shortly after this, the protagonist is attacked by a Dark Summoner named Sid Davis. Killed by Davis, he is returned to the land of the living by Charon. Upon waking, the protagonist finds himself in the body of Kuzunoha, who was also killed by Davis. Now trapped in Kuzunoha's body, the protagonist is forced to work in his place to investigate the reasons behind Sid Davis' activities alongside Kuzunoha's partner Rei Reiho: he does this to both protect the city and return Kuzunoha and himself to their original bodies.

During his investigations, the protagonist and Rei learn of multiple demon-run criminal organizations causing chaos in Hirasaki including factions of the Yakuza, all of them connected to Davis. The protagonist's efforts against the demon threats are hindered by Hideo Momochi, who accuses the pair of being involved in the incidents until the police station is infested by demons and the police chief is revealed to be a demon in disguise. The protagonist also foils an attempt to Kumiko for unknown reasons. After taking down each of the five major demon factions, Davis reveals that the entire affair was orchestrated to break five seals holding prisoner the spirit of Inaruna: once a powerful regional priestess who was executed for resisting the forces of Emperor Jimmu with her magical powers during the unification of Japan, her spirit's hatred for her conquerors has grown beyond control and she will destroy the city if released. Kumiko, the reincarnation of Inaruna, is successfully abducted by Davis and used as a host for Inaruna's spirit. Although she is summoned, the protagonist and Rei rescue Kumiko and kill Davis. They then successfully defeat Inaruna. With the city returned to normal, the protagonist remains trapped in Kuzunoha's body, and can choose either to use his own name or adopt the Kuzunoha title.