苏氨酸（Threonine）是一种必需的氨基酸，为白色斜方晶系或结晶性粉末，微甜。因结构与苏糖相似而得名。主要用于医药、化学试剂、营养强化剂，可以强化乳制品，具有恢复人体疲劳，促进生长发育的效果。L-苏氨酸是一种饲料的原料。

Threonine (abbreviated as Thr or T) encoded by the codons ACU, ACC, ACA, and ACG is an α-amino acid that is used in the biosynthesis of proteins. It contains an α-amino group (which is in the protonated −NH+
3 form under biological conditions), an α-carboxylic acid group (which is in the deprotonated −COO form under biological conditions), and an alcohol containing side chain, classifying it as a polar, uncharged(at physiological pH) amino acid. It is essential in humans, meaning the body cannot synthesize it, and must be ingested in our diet. Threonine is synthesized from aspartate in bacteria such as E. coli.