In Greek mythology, Thaumas (/ˈθɔːməs/; Θαύμας; gen.: Θαύμαντος) was a sea god, son of Pontus and Gaia, and the full brother of Nereus, Phorcys, Ceto and Eurybia. According to Hesiod, Thaumas' wife was Electra, one of the Oceanids, the many daughters of the Titans Oceanus and Tethys, by whom he fathered Iris, the messenger of the gods, and the Harpies.
The names of Thaumas' Harpy daughters vary. Hesiod and Apollodorus name them: Aello and Ocypete. Virgil, names Celaeno as one of the Harpies. However while Hyginus, Fabulae Preface has the Harpies, Celaeno, Ocypete, and Podarce, as daughters of Thaumas and Electra, at Fabuale 14.18, the Harpies are said to be named Aellopous, Celaeno, and Ocypete, and are the daughters of Thaumas and Ozomene.
The late 4th-early 5th century poet Nonnus gives Thaumas and Electra two children, Iris, and the river Hydaspes.
Plato associates Thaumas' name with θαῦμα ("wonder").
Thaumas was also the name of a centaur, who fought against the Lapiths at the Centauromachy.