Galaxy Arena

Galaxy Arena is a galaxy-based court in Mario Tennis Open. It has objects from Super Mario Galaxy, such as Shrinking Tiles, a Launch Star, Star Bits, a planet from the Gateway Galaxy, a Black Hole, Turquoise, Red and Green Lumas, and the whole Comet Observatory in the distance. The special game Galaxy Rally is played on this court, where the Star Chips appear on the court, and the player may try to collect them by hitting the tennis ball at them to receive coins. It is an unlockable stage, and it can be unlocked by completing the Final Cup in the Star Open Tournament.

The unlockable stage has differences from the one played in Galaxy Rally; it lacks the disappearing green platforms and it takes place in an another location. Also, it has max bounce and max speed. There are two varieties to this court: the Morph and the Crystal court. The Crystal court plays normally, but the Morph court has an added gimmick. When the player performs a chance shot, and the ball hits the ground, the surface on the opponent's side of the court changes, using various types from other courts in this game, which affect ball velocity and bounce. A unique surface with a black hole pattern erratically makes the ball bounce into one extreme direction. While this surface is used in all rounds of the Final Cup, different sets of three other surfaces are used in each round. The starting round uses the hard, mushroom, and stone surfaces. The clay, ice, and wood surfaces are used in the semifinals, and the final round uses the grass, carpet, and sand surfaces. Only one side of the court can get altered: the player must perform a chance shot to change the surface on the opponent's side, thereby returning their own side to normal.