2-Methyl-1-butanol (IUPAC name, also called active amyl alcohol) is an organic compound with the formula CH3CH2CH(CH3)CH2OH.

This colorless liquid occurs naturally in trace amounts and has attracted some attention as a potential biofuel, exploiting its hydrophobic (gasoline-like) and branched structure.

Also, it is one of the many components of the aroma of various fungi and fruit, e.g., the summer truffle, tomato,[4] and cantaloupe.

2-Keto-3-methylvalerate, a precursor to threonine, is converted to the target alcohol by the sequential action of 2-keto acid decarboxylase and dehydrogenase.

[7] It can be derived from fusel oil (because it occurs naturally in fruits such as grapes[8]) or manufactured by either the oxo process or via the halogenation of pentane.