Duct tape (also called duck tape, from the cotton duck cloth it was originally made of) is cloth- or scrim-backed pressure-sensitive tape, often coated with polyethylene. There are a variety of constructions using different backings and adhesives, and the term 'duct tape' has been genericized to refer to different cloth tapes with differing purposes. A variation is heat-resistant foil tape useful for sealing heating and cooling ducts, produced because the adhesive on standard duct tape fails and the synthetic fabric reinforcement mesh deteriorates when used on heating ducts.

Duct tape is generally silvery gray in color, but also available in other colors and printed designs, from whimsical yellow duckies to practical camouflage patterns. It is often confused with gaffer tape (which is designed to be non-reflective and cleanly removed, unlike duct tape).

During World War II, Revolite (then a division of Johnson & Johnson) developed an adhesive tape made from a rubber-based adhesive applied to a durable duck cloth backing. This tape resisted water and was used to seal some ammunition cases during that period.

"Duck tape" is recorded in the Oxford English Dictionary as having been in use since 1899; "duct tape" (described as "perhaps an alteration of earlier duck tape") since 1965.