A chaise longue (; French: [ʃɛz lɔ̃ɡ], "long chair") is an upholstered sofa in the shape of a chair that is long enough to support the legs of the sitter.

In modern French the term chaise longue can refer to any long reclining chair such as a deckchair. A literal translation in English is "long chair". The term chaise lounge, used since (1800) is corruption of French chaise longue "long chair," with French word order; the second word confused in English with lounge.

An alternative spelling for the chaise (chair) is chaise lounge and pronounced , a folk etymology replacement of part of the original French term with the unrelated English word lounge. When English speakers imported a new kind of sofa from France in the late 1700s, they transformed the name 'chaise longue' ("long chair") into 'chaise lounge'—since 'lounge' is an English word spelled with the same letters and lounging is something one can do on a "chaise longue." The use of the alternative spelling, namely, chaise lounge has been documented both in British texts since at least 1811 and in American texts since 1824.