Nether Fortress is a large structure found in the Nether, made of nether bricks and composed of bridges, corridors, stairways, and towers. It is the only place where blazes, wither skeletons, and Nether wart naturally generate, making it essential for brewing and fighting the Wither.

Fortresses generate in all Nether biomes and share regional generation space with bastion remnants. Only one of these structures can appear per region, with fortresses more common in basalt deltas.

The structure includes blaze spawner platforms, Nether wart gardens, and loot chests placed in corridor turns. Chests can contain items like gold, iron, diamonds, saddles, and horse armor.

Unique mob spawning rules apply: blazes, wither skeletons, zombified piglins, magma cubes, and skeletons spawn at higher rates within fortress boundaries. In Java Edition, spawning depends on structural bounding boxes and nether brick floors. In Bedrock Edition, mobs spawn along defined spawn lines inside the structure.

Nether fortresses are key to game progression due to blaze rods, needed for brewing and reaching the End.