A jack-o'-lantern (or jack o'lantern) is a carved lantern, most commonly made from a pumpkin or a root vegetable such as a rutabaga or turnip. Jack-o'-lanterns are associated with the Halloween holiday. Its name comes from the reported phenomenon of strange lights flickering over peat bogs, called will-o'-the-wisps or jack-o'-lanterns. The name is also tied to the Irish legend of Stingy Jack, a drunkard who bargains with Satan and is doomed to roam the Earth with only a hollowed turnip to light his way.

Jack-o'-lanterns carved from pumpkins are a yearly Halloween tradition that developed in the United States when Celtic Americans brought their root vegetable carving tradition with them. It is common to see jack-o'-lanterns used as external and internal decorations prior to and on Halloween.

To make a jack-o'-lantern, the top of a pumpkin or turnip is cut off to form a lid, the inside flesh is scooped out, and an image—usually a "scary" or "funny" face—is carved out of the rind to expose the hollow interior. A light source, traditionally a flames from a candle or tealight, is placed within before the lid is closed. Artificial jack-o'-lanterns with electric lights are also marketed.