Bracken (Pteridium) is a genus of large, coarse ferns in the family Dennstaedtiaceae. Ferns (Pteridophyta) are vascular plants that have alternating generations, large plants that produce spores and small plants that produce sex cells (eggs and sperm). Brackens are noted for their large, highly divided leaves. They are found on all continents except Antarctica and in all environments except deserts; though their typical habitat is moorland. The genus probably has the widest distribution of any fern in the world.

In the past, the genus was commonly treated as having only one species, Pteridium aquilinum, but the recent trend is to subdivide it into about ten species.

As ferns, brackens do not have seeds or fruits, but the immature fronds, known as fiddleheads, are edible.

The word bracken is of Old Norse origin, related to the Swedish word bräken, meaning fern.