In Greek mythology, Themisto (; Ancient Greek: Θεμιστώ, romanized: Themistṓ, lit. 'belonging to the law or customs') may refer to the following women:
Themisto, one of the 50 Nereids, marine-nymph daughter of the sea divinities Nereus and the Oceanid Doris.
Themisto, daughter of the river god Inachus and the mother of Arcas by Zeus.
Themisto, daughter of the Hyperborean king Zabius, mother of Galeos by Apollo.
Themisto, the third and last wife of Athamas.