Mario Circuit (マリオサーキット Mario Sākitto) is a playable stage in Super Smash Bros. Brawl.
 Stage Description
The stage has a simple layout, with a one base platform that extends all the way off the stage, and three floating platforms above it, arranged in a trapezoid shape. Every so often, Shy Guys in go-karts will drive from the background through the stage via the lower road, similar in concept to the F-Zero-themed stages Mute City and Port Town Aero Dive. They will also sometimes fly over the platforms on the upper road from the left, though players are alerted beforehand by a flashing warning arrow, akin to Onett. If characters are struck by the karts, they will take 15% damage and neutral knockback and can even be Star KO'd at higher percentages. Additionally, the screen in the background will show the location of the Shy Guys on the circuit, making it possible to avoid the racers. The Shy Guys can be attacked and sent spinning out to the side of the screen.
Interestingly, there are graphics for the entire track. Visuals are inaccessible, even when pausing and changing the camera angle. However, such angles can be viewed by hacking.
This was the last stage that was first shown in trailers to be confirmed on the DOJO!!. Over a year had passed since its initial revelation, making Mario Circuit the stage with the longest duration between its trailer and DOJO!! confirmations.
 Tournament Legality
Mario Circuit is banned in tournaments due to chain-grabbers being able to chain throw an opponent off of the stage's sides. In addition, the cars are overly powerful stage hazards, and gameplay centers around avoiding the cars, as well as throwing opponents into them.
While using Link or Toon Link's Triforce Slashes, if a Shy Guy is hit by the final strike and only the final strike of the Final Smash, the Shy Guy will continue to go around the circuit but it will be in slow motion. It will still show the kart's position on the monitor in the background but it will be far behind the group. Even though it is moving so slow, it will still deal normal damage and knockback.
Mario Circuit is a track that is in every Mario Kart ever since the original Super Mario Kart; however, there are only a small amount resemblances in this stage to any of the Mario Circuits. One of these resemblances is in Super Mario Kart's Mario Circuit 2, which has a jump that overlaps another part of the track. The Shy Guys in this stage having to jump over the road onto to the other side could be a reference to Mario Circuit 2's jump. However, in Mario Kart DS, Shy Guys only appear in DS Download Play. Another resemblance is that in Mario Kart 64's Mario Circuit, there are giant mushrooms for decoration. Tall mushrooms can be seen in the background of this stage, but the mushrooms are much thinner and taller compared to the ones in Mario Kart 64.
The overall design of this stage resembles Figure-8 Circuit in Mario Kart DS. Figure-8 Circuit features a seating area for spectators, pipes in the background, and giant block structures (which originally appeared in Super Mario Bros. 3). Also a small sign that says "Nintendo" is seen in this race track. All these features, including the "Nintendo" sign, are retained in this stage, but Figure-8 Circuit only had one seating area while this stage features two. Also, in Mario Kart DS, if friends wanted to play the game together, but somebody didn't have it, they could still connect together through DS Download Play; however, the people who didn't have the game have no choice but to play as a Shy Guy. This stage features the drivers as Shy Guys and this could be also be a reference to Mario Kart DS. The trees that have faces in this stage are possibly a reference to the trees in Mario Kart: Double Dash.
The design of the giant screen in the background is based on the map that was displayed on the DS Touch Screen during races in Mario Kart DS. Pressing the "Y" button or tapping the screen with the stylus gave the player this view, along with the location and position of every racer. All these features are retained here.