A ponytail is a hairstyle in which some, most, or all of the hair on the head is pulled away from the face, gathered and secured at the back of the head with a hair tie, clip, or other similar device, and allowed to hang freely from that point. It gets its name from its resemblance to the undocked tail of a horse or pony.

Ponytails are most commonly gathered at the middle of the back of the head, or the base of the neck. Depending on fashions, they may also be worn at the side of the head (which is sometimes considered formal) which is worn over one ear, or on the very top of the head (allowing the hair to fall down the back or one side of the head).

If the hair is divided so that it hangs in two sections they are bunches or pigtails if left loose, or pigtails or braids if plaited. Unbraided ponytails worn above each ear are sometimes called dog-ears.