Yoshi's Island (race course)

Yoshi's Island is a race course that first released as part of Wave 4 of the Booster Course Pass in Mario Kart 8 Deluxe, appearing as the fourth and final course of the Fruit Cup, and reappears in Mario Kart Tour, starting with the 2023 Yoshi Tour. It is a course that takes place on the island it is named after, with its music theme being an arrangement of the athletic theme from Super Mario World 2: Yoshi's Island. It is the second course to be introduced to the Mario Kart series in the Booster Course Pass, after Sky-High Sundae. Despite the course being introduced in Mario Kart Tour around one month after its Booster Course Pass release, internal data marks it as a new course for Mario Kart Tour.

Akin to other courses based on games outside of the Mario series, this course uses the logo for the Yoshi's Island series for its starting line, and the course itself is heavily inspired by the game it is based on, featuring obstacles like Stilt Guys and Huffin Puffins, and mechanics like Winged Clouds that can summon stretches of road when driven into. The layout of the course appears to reference all the world themes from Super Mario World 2: Yoshi's Island. Many cameos from the game appear in the background, including Incoming Chomps, Petal Guys, Goonies, an enormous Nep-Enut, and Yoshi's ally Poochy. Koopa Paratroopas and Sidesteppers also appear on the course. A near the starting line plays the same sound effect as the Paddle Platforms in Super Mario World 2: Yoshi's Island. Additionally, there is a Goal Ring near the finish line.

Similarly to Hyrule Circuit, Animal Crossing, and Urchin Underpass, this course has unique coins—in this case, the coins have the same design and collection sound effect as in the Yoshi's Island series. It also has a unique race fanfare, victory theme, and results theme based on the "Game Start", "Goal", and "Score" themes, respectively. While some other courses feature unique fanfares and results music, this is the only course in the Mario Kart series to feature its own unique victory theme. The icon for this course resembles the title screen for Super Mario World 2: Yoshi's Island.

Excluding courses announced simultaneously, this course and Piranha Plant Cove mark the shortest period of time between the announcement of two new courses for the Mario Kart series, with them being announced five days apart from each other.

Mario Kart 8 Deluxe
Racers begin at Yoshi's House in a field that resembles World 1 from Super Mario World 2: Yoshi's Island. Racers race along a slight serpentine path, avoiding Stilt Guys before diving into an underwater section. Surrounding the underwater section is a forest that resemble the basis' World 2 and World 3. This section ends with racers driving into a castle. Leaving the castle, racers emerge from the water and drive through a small cave. Exiting the cave, racers drive up an active volcano, like the one in World 6. A glider ramp then takes players up to the clouds, driving above snow-capped mountains similar to World 5, before taking another glider to the ground level where they can drive into a Winged Cloud to make a red bridge appear. After reaching the ground (or the aforementioned bridge), they make a right hand turn to return to the finish line.

In Time Trial ghost replays, the bridge does not appear when driving into the Winged Cloud, including both staff ghosts' replays. However, its collision is still present. The reason for this is likely connected to the same reason why coins do not disappear during Time Trial ghost replays, as they are not collected by a physical character.

Mario Kart Tour
Yoshi's Island reappears in Mario Kart Tour, debuting in the 2023 Yoshi Tour. The minimap for the course is rotated 90° clockwise compared to how it appeared in Mario Kart 8 Deluxe. While the Coins are no longer themed around Yoshi Coins, other crossover elements like the Yoshi's Island starting banner, the race fanfare and the unique race ending theme have been retained, making it the first course in Mario Kart Tour to feature these elements. Instead of acting as obstacles, the Huffin Puffins are now located in the background as spectators. The road leading up to the top of the mountain after leaving the castle section now features an icy fog effect. The Cloud Platform after the gliding section over the volcano is bouncy and lacks the ramp. The Winged Cloud is now stationary instead of moving from left to right and vice-versa. The arrangement of coins inside the Flower Ring has been removed, though it now provides points when passed through. Poochy has also been removed from the mailbox right after the finish line, most likely due to him debuting as a driver alongside the release of the course. The last hill in the row of background hills now has a set of pine trees on its top, now resembling the hills in World 2-1 of the original Yoshi's Island more closely. Unlike in Mario Kart 8 Deluxe, the volcano is dormant, with no lava splashes occurring. Additionally, the chimneys on Yoshi's House as well as on the castle in the cloud section now emit smoke.

This course also appears as Yoshi's Island R (reversed), Yoshi's Island T (with ramps), and Yoshi's Island R/T (reversed with ramps). The logo for the T variant's starting line above the main starting line uses the classic Mario Kart logo as opposed to the other new courses, presumably due to Super Mario World 2: Yoshi's Island being an SNES game. In the R variant, Stilt Guys are present on the uphill U-bend.

This course is a favorite of Orange Shy Guy, Yoshi, Red Yoshi, Yoshi (Egg Hunt), Shy Guy (Ninja), Yellow Shy Guy (Explorer), Poochy, Dr. Mario, and the Reindeer, White, Yoshi, Silver, Petey Piranha, and Pastry Chef Mii racing suits.