Sylph (also called sylphid) is a mythological spirit of the air. The term originates in the 16th century works of Paracelsus, who describes sylphs as invisible beings of the air, his elementals of air.

Since the term sylph itself originates with Paracelsus, there is relatively little pre-Paracelsian legend and mythology that can be confidently associated with it, but a significant number of subsequent literary and occult works have been inspired by the idea. Robert Alfred Vaughan noted that "the wild but poetical fantasies" of Paracelsus had probably exercised a larger influence over his age and the subsequent one than is generally supposed, particularly on the Rosicrucians, but that through the 18th century they had become reduced to "machinery for the playwright" and "opera figurantes with wings of gauze and spangles."