In the field of translation, a translation unit is a segment of a text which the translator treats as a single cognitive unit for the purposes of establishing an equivalence. The translation unit may be a single word, or it may be a phrase, one or more sentences, or even a larger unit.

When a translator segments a text into translation units, the larger these units are, the better chance there is of obtaining an idiomatic translation. This is true not only of human translation, but also in cases where human translators use computer-assisted translation, such as translation memories, and also when translations are performed by machine translation systems.