Spandex, Lycra, or elastane is a synthetic fiber known for its exceptional elasticity. It is a polyether-polyurea copolymer that was invented in 1958 by chemist Joseph Shivers at DuPont's Benger Laboratory in Waynesboro, Virginia, US.

The generic name "spandex", which is an anagram of the word "expands", is the preferred name in North America. In continental Europe, it is referred to by variants of "elastane", including élasthanne (France), Elastan (Germany, Sweden), elastano (Spain), elastam (Italy), and elastaan (Netherlands); and in the UK, Ireland, Portugal, Spain, Latin America, Australia, and New Zealand, it is primarily known as "Lycra".

Brand names for spandex include Lycra (made by The Lycra Company, previously a division of DuPont Textiles and Interiors), Elaspan (The Lycra Company), Acepora (Taekwang Group), Creora (Hyosung), INVIYA (Indorama Corporation), ROICA and Dorlastan (Asahi Kasei), Linel (Fillattice), and ESPA (Toyobo).