Polytetrahydrofuran, also called poly(tetramethylene ether) glycol or poly(tetramethylene oxide), is a collection of chemical compounds with formula HO(CH2)4O(CH2)4)nOH or HO((CH2)4O-)n-H.

The product is commercially available as polymers of low average molecular weights, between 250 and 3000 daltons.

The product is sold under various trade names including Terathane from Invista[1] and PolyTHF from BASF.

[2] The BASF plant in Ludwigshafen at one point was producing 250,000 metric tons per year.

[3] The main use of polytetrahydrofuran is to make elastic fibres such as spandex (elastane) for stretchable fabrics[4] and for polyurethane resins.