Acorn Plains is the grassy first world of New Super Mario Bros. U. It lies south of Layer Cake Desert, west to Sparkling Waters, Soda Jungle and Rock-Candy Mines, and south-west of Frosted Glacier, Meringue Clouds and Peach's Castle. It is a plains world with acorn trees, blue-green hills, shrubs, jagged mountains reminiscent of some of the backgrounds in Super Mario World and the world's most defining feature, the Acorn Tree. This special tree is one of main sources of the game's new power-up, the Super Acorn. It can be found in the game's intro, Acorn Plains' map section and said world's first level. This world has eight levels, with 5 normal levels, a secret level, a Tower level and a Castle level, a red and green Toad House, a Piranha Plant Enemy Course, and a spot where a magenta Baby Yoshi walks near. The Castle boss of this world is Lemmy Koopa.
 New Super Mario Bros. U
- A course with Spine Coasters of various lengths.
- A course with rising ledges.
 Names in Other Languages
Donguri e i gen
||Plaine du Grand Chênes
||Big Oak Plains
||Piana delle ghiande
||Planície das Bolotas
The early World Map of Acorn Plains, displaying Miiverse in the game.
- In early builds of New Super Mario Bros. U, the Acorn Plains map looks substantially different. The map was significantly less detailed, the Acorn Trees did not show the Super Acorns, the map had two red Toad Houses, and the green Toad House was in a different spot, there are two Enemy Courses instead of one, a secret exit was planned to appear in Yoshi Hill which revealed a bridge to Lemmy's Swingback Castle and the spot where the Balloon Baby Yoshi was, is gone.
- Previous footage of the Acorn Plains map have depicted the pipe that the Piranha Plant is nesting in as green, instead of red.
 New Enemies