Rabbid Mario is a Rabbid dressed as Mario, and one of the eight main heroes in Mario + Rabbids Kingdom Battle. He was created when Spawny used the SupaMerge to fuse a Rabbid with a Mario Cap. In Mario + Rabbids Kingdom Battle, Rabbid Mario teams up with Mario, Luigi, Princess Peach, Yoshi, Rabbid Luigi, Rabbid Peach, and Rabbid Yoshi to save the Mushroom Kingdom from Rabbid-fused enemies and Bowser Jr.'s attempted takeover.
Aside from the introductory cutscene detailing his creation, Rabbid Mario is first found frozen in Sherbet Desert. With Toad's help, he is thawed after the battle with Blizzy and Sandy, joining the crew on their adventure.
In-game, he is described as a Brawler with great offense and mobility, but poor defense. His primary weapon is a Boomshot, and his secondary weapon is a Melee, making him effective at close-range combat and area attacks. His "Boom Dash" allows him to create shockwaves when he dashes into a foe, harming anyone (enemy or ally) within the blast radius for a percentage of the damage inflicted on his main target. His special abilities include Bodyguard, a barrier that reduces the damage he takes from movement-based attacks (such as dashes or Team Jumps), and Magnet Dance, which forces enemies within its range to move towards Rabbid Mario. His Magnet dance can also be used with "line-of-sight techniques" as well as other forced movement abilities or weapons that have a high chance of inflicting Burn, Push, or Bounce to force nearby enemies out of hiding and deal extra damage. His Bodyguard ability can also be used with Peach's Protection ability to reduce damage Rabbid Mario takes from both movement-based damage and weapon-based damage. His Boom Dash can also be used in tandem with Mario's M-power to increase damage.
Similar to most Rabbids, Rabbid Mario is playful, mischievous, curious, and reckless. He likes mimicking Mario, and tends to show-off his strength. He is fearless, adventurous, and will not back down from a challenge. Rabbid Mario seems to have an ear for music as he performed his own version of the Super Mario Bros. theme song. This can also be recognized in his victory animation, which has him strum a small tune that resembles that of losing a life in Super Mario Bros. 3, as well as some of his voice clips used in-game, which reference the 'Lose a Life' and '1-UP' jingles from Super Mario Bros.