An eyelash or simply lash is one of the hairs that grow at the edge of the eyelid. Eyelashes perform some of the same function as whiskers do on a cat or a mouse in the sense that they are sensitive to being touched, thus providing a warning that an object (such as an insect) is near the eye. Eyelashes may also be fluttered, as a form of non-verbal communication.

Beautiful, long eyelashes are considered a sign of femininity in most if not all cultures, and so their appearance is sometimes enhanced with mascara. The twentieth century saw the beginning of convincing-looking false eyelashes, popular in the 1960s.

Eyelashes are prone to a number of problems:

• Madarosis is the loss of eyelashes
• Blepharitis is the irritation of the lid margin (where eyelashes join the eyelid). The skin often becomes flaky.
• Trichiasis is ingrown eyelashes
• Eyelashes may become infested with crab louse parasites
• An eyelash may become infected and form a stye.

Inherited eyelash problems are common in some breeds of dogs.