Geno (Japanese: ジーノ, Hepburn: Jīno) is a character who first appeared in Square's 1996 role-playing video game Super Mario RPG: Legend of the Seven Stars, which was published by Nintendo for the Super Nintendo Entertainment System. Geno is the name of a doll dressed in a blue hat and cape, which becomes inhabited by a being from the stars known as a Star Warrior. Geno is introduced as one of the game's party members who fights alongside Mario to stop the game's main antagonists, the Smithy gang.

In Super Mario RPG, Geno is able to use both physical attacks such as blasters as well as a wide array of magic attacks, with some commenting that the character is similar to wizard roles in other role-playing video games. Outside of Super Mario RPG, the character has made only small cameo appearances in other games, such as Mario & Luigi: Superstar Saga and as a costume for Mii Fighters in the crossover fighting game series Super Smash Bros..

Despite Geno's limited game appearances due to copyright issues, he received acclaim among both critics and fans of the game, with some stating he is the highlight of Super Mario RPG's story and describing him as having a cool and mysterious personality. A cult following for the character has made many fans petition for Geno's inclusion in future games, including as a playable fighter in future Super Smash Bros. titles.

Geno is a star warrior from a place he calls Star Road, which is said to grant wishes. Geno's true form is never revealed in any of his appearances but is said to be a star with a name represented with the symbols "♡♪!?", which no one can understand. When descending from Star Road to help Mario and his friend, he decides to inhabit the body of a wooden doll called Geno, owned by a Toad named Gaz. The star warrior decides to adopt the name of the doll. The design of the doll has a blue hat and cape, with two red strips poking through the hat.

In battle, Geno has often been described as a "glass cannon" with high attack power and low defense. While in combat, Geno is able to swap out his hands for finger cannons or a blaster, which he can use to shoot beams or stars. Additionally, Geno has access to a range of magic attacks. With the move "Geno Whirl", he can send out large magical discs that can deal massive damage, and are even able to instantly kill a boss. With "Geno Flash", he can transform into a large cannon that is able to fire at all enemies in a battle. Finally, using the support ability "Geno Boost", he can increase the attack and defense stats of another party member.

Geno's appearance was initially conceptualized by Yuka Miyamoto. The rough draft was sent over to Kazuyuki Kurashima to be further developed. In 2020, Kurashima revealed initial concept art for Geno that depicts him with a knightly appearance; Kurashima gave him a taller stature, plate armor around the face and body, spiky hair, and a sword. A more finalized version of Geno was later designed by Hideo Minaba, featuring his hat and cape, although still brandishing a sword. According to Kurashima, Geno's design was finalized by both Minaba and Miyamoto.

Geno's first appearance is in 1996's Super Mario RPG: Legend of the Seven Stars as one of the game's five party members. As a guardian and star warrior of the Star Road, he is sent to the Mushroom Kingdom by a "higher authority" to fix the Star Road and restore its powers to grant wishes after it was destroyed by the game's main antagonists, the Smithy Gang. Upon arriving in the settlement of Rose Town, he begins to inhabit a wooden puppet named Geno; choosing him as he believes him to be the strongest of the dolls in the room. Mario and his partner Mallow follow the puppet into the nearby Forest Maze to which he gives the player indirect help as to where to go. At the end of the Forest Maze, Geno faces off against Bowyer, a member of the Smithy Gang. After Mario saves Geno from one of Bowyer's attacks, the pair and Mallow defeat Bowyer to claim his Star Piece, the game's main collectable which is key to fixing Star Road. After introducing himself to Mario and Mallow, Geno decides to team up with the pair in order to search for the remaining Star Pieces in order to fix the Star Road. At the end of the game, Geno and the other party members confront Smithy in his lair. After defeating Smithy, Geno decides to return to Star Road and takes the Star Pieces with him. Upon leaving, all that remains in his place is the now uninhabited puppet.

Geno retains the same role in the 2023 remake Super Mario RPG. In the remake, he gains a new weapon that is only available in the postgame. A new mechanic was introduced called "Triple Moves" which allows all party members in battle to use a powerful attack. An example of this is the move "Star Riders", which is an attack performed by Geno, Mario and Mallow that does significant damage to one enemy at a time. Another new feature added to the remake is a scrapbook where events from the game are logged by Geno, as well as Mallow.