Mario Bros. is an unlockable stage in Super Smash Bros. Brawl. It is based on the location in the 1983 arcade game Mario Bros.. The stage reappears in Super Smash Bros. Ultimate. In Super Smash Bros. Brawl, R.O.B. is fought here upon being unlocked once certain requirements have been fulfilled, unless he is unlocked through the Subspace Emissary.
In Brawl, the course is initially hidden and must be unlocked before players can make use of it. To do this, "Event 19: Wario Bros" must be completed. This event match involves Wario fighting Mario and Luigi, who are on a team. Once defeated, the event will be cleared and the stage will be unlocked for use in other game modes.
Similar to the other arcade retro stage 75m (from Donkey Kong), Mario Bros. is an identical rebuild of the stage as it appeared in the original Mario Bros.. Matches played in the course require different strategies from typical courses, it is nearly impossible to normally knock a opponent out due to its low ceilings.
Sidesteppers are slightly stronger than Shellcreepers in all three levels. Fireballs may also show up, bouncing around the stage and damaging anyone they touch. All three enemies are featured as 2D sprites. The Fighter Fly does not appear in this stage, and similarly, Freezies do not serve as stage obstacles, due to them serving as normal items in the game.