紫萁属是蕨类植物门中的一属，为主要的温带蕨类。五至十个物种被归在此属中。

其物种有完全同种二形的蕨叶。因为大量的孢子囊会在同一时期成熟，并显现出艳丽的金黄色，让孢子囊看起来像是花一样，所以此属有时会被称之为「开花蕨」。

紫萁属的物种会被鞍形埃尺蛾之类的鳞翅目幼虫食用。

Osmunda is a genus of primarily temperate-zone ferns of family Osmundaceae. Five to ten species have been listed for this genus.

The species have completely dimorphic fronds or pinnae (hemidimorphic), green photosynthetic sterile fronds, and non-photosynthetic spore-bearing fertile pinnae, with large, naked sporangia. Because of the large mass of sporangia that ripen uniformly at the same time to a showy golden color, the ferns look as if they are in flower, and so this genus is sometimes called the "flowering ferns".