GBA Bowser's Castle 3

Bowser's Castle 3 (known as Bowser Castle 3 prior to Mario Kart Tour) is the final course of the Star Cup in Mario Kart: Super Circuit. It reappears in Mario Kart Wii as the second course of the Leaf Cup and in Mario Kart Tour starting from the Bowser Tour. Like all other Bowser Castle courses, it features sharp 90 degree turns and jumps over pits of lava. Kamek can also be seen flying back and forth near the finish line. The course takes place on the exterior of the castle, with storm clouds and lightning visible in the background. In Mario Kart: Super Circuit, the course shares its music with the other three Bowser Castles: 1, 2, and 4.

Course layout
The track starts with a turn to the left after the starting line, leading to a straight section of track containing the first set of Item Boxes and Coins which narrows after passing a Lava grid. The track then takes another left turn past two Thwomps, and then turns to the right over a pair of lava grids with more coins. The track then takes another right towards some coins and then makes a U-turn to the left over another grid featuring a pair of Thwomps. The track then passes over a number of small Ramps over the lava moving slightly to the right, with Lava Bubbles occasionally jumping up from the lava. The track passes another two Thwomps, with an Item Box behind the first one approached, and makes a U-turn to the left, leading to three more Thwomps and several more coins. The track heads to the right and passes over another grid in the lava, now with holes in it through which Lava Bubbles can occasionally jump, and then follows a zig zag shape to the right featuring more coins and Item Boxes. The track then makes a final turn to the left past another pair of Thwomps and over another lava grid with holes before returning to the starting line.

Mario Kart Wii
Bowser Castle 3 reappears in Mario Kart Wii as the second track of the Leaf Cup. The track is now a paler gray rather than blue, and the banners of Bowser in the background are now black with red faces, and Kamek has been removed from the track entirely. The track now features patches of mud that slow the player down on most of the track's corners, and all of the coins have been removed. Each set of Item Boxes now feature a larger number of Item Boxes, with several additional single boxes appearing behind Thwomps, Item Boxes occasionally appearing instead of Lava Bubbles on the jump section, extra sets being added on the corner after the jumps and after the zig zag section, and a moving set on the first grid with holes. A Dash Panel ramp has also been added on the left U-turn after the smaller ramps, with the Thwomps being slightly rearranged to suit the new layout. A shortcut can be performed by aiming left at the last yellow ramp and using a Mushroom.

Tournaments
In Mario Kart Wii, a tournament took place on this track. Players had to go through a total of 30 gates, and were restricted to only using karts. It was the second tournament of February 2009, but its information was accidentally given for February 2009's first tournament, which took place at Block Plaza and had a different objective. This tournament was repeated as the second tournament of February 2011, the first tournament of June 2012, and the second tournament of August 2013.

Mario Kart Tour
Bowser's Castle 3 reappears in Mario Kart Tour, starting with the Bowser Tour. Instead of having a unique appearance, the course now reuses the visuals of the other two GBA Bowser's Castle courses in this game, and has a starting banner with the classic Mario Kart logo. More ramps have been added to the course, most notably on the bridge at the end, which was slightly redesigned. All offroad sections and the additional ramp added in Mario Kart Wii have been removed. The diagonal portion of the track has also been reworked to be wider and shorter. The coins have been re-added to the course, and Item Boxes can no longer appear instead of Lava Bubbles. The course is a favorite of Mario (Samurai), Daisy (Farmer), Cat Mario, Daisy (Thai Dress), Meowser, and the Bowser Mii Racing Suit. It is also a favorite of Luigi (Knight) if he reaches level 3.

As with other courses in the game, Bowser's Castle 3 has a reverse variant, a trick variant, and a reverse/trick variant, referred to as Bowser's Castle 3R, Bowser's Castle 3T, and Bowser's Castle 3R/T respectively. The reverse/trick variant was added in the 2023 New Year's Tour; unlike most other trick and reverse/trick variants in the game, the ramps added to the track are more haphazard in their composition. Like the other GBA Bowser's Castle courses in the game and RMX Bowser's Castle 1, this course reuses Mario Kart 7's arrangement for GBA Bowser's Castle 1.

For this course's tour appearances, see List of GBA Bowser's Castle 3 tour appearances in Mario Kart Tour.

Mario Kart Wii

 * European website bio: "Thunder clouds are gathering on the horizon as you race across huge cobbles and attempt to twist round one sharp corner after another. And if that doesn't scare you, then maybe the massive Thwomps will!"