Biomes are distinct regions in 99 Nights in the Forest that players can explore, each featuring unique environments, exclusive structures, and biome-specific items, enemies, and resources that encourage exploration and varied gameplay strategies.
| Biome Name | Image | Entities | Items |
| Forest Biome |  | Bunny Wolf Alpha Wolf Bear Cultists The Deer Frogs Missing Children Pelt Trader Fairy Horse Furniture Trader Aliens The Owl The Ram | Various |
| Snow biome |  | Arctic Fox Polar Bear Mammoth The Owl | Various |
| Volcanic Biome |  | Scorpion Cultists The Ram Hellephant King Cultist | Various |
| North Pole Biome |  | Mammoth Christmas Elves | Various |
| Fairy Mini-Biome |  | Fairy Fairy Wolf | Various |