Deuterated tetrahydrofuran (d<sub>8</sub>-THF) is a colourless, organic liquid at standard temperature and pressure. This heterocyclic compound has the chemical formula C<sub>4</sub>D<sub>8</sub>O, and is an isotopologue of tetrahydrofuran. Deuterated THF is used as a solvent in NMR spectroscopy, though its expense can often be prohibitive.