Alcyone (/ælˈsaɪ.əniː/; Ancient Greek: Ἀλκυόνη, romanized: Alkyóne), in Greek mythology, was the name of one of the Pleiades, daughters of Atlas and Pleione or, more rarely, Aethra. She attracted the attention of the god Poseidon and bore him several children, variously named in the sources: Hyrieus, Hyperenor, and Aethusa; Hyperes and Anthas; and Epopeus. By a mortal, Anthedon, Alcyone became the mother of the fisherman Glaucus, who was later transformed into a marine god.

Alkyóne comes from alkyón (ἀλκυών), which refers to a sea-bird with a mournful song or to a kingfisher bird in particular. The meaning(s) of the words is uncertain because alkyón is considered to be of pre-Greek, non-Indo-European origin. However, folk etymology related them to the háls (ἅλς, "brine, sea, salt") and kyéo (κυέω, "I conceive"). Alkyóne originally is written with a smooth breathing mark, but this false origin beginning with a rough breathing mark (transliterated as the letter H) led to the common misspellings halkyón (ἁλκυών) and Halkyóne (Ἁλκυόνη), and thus the name of one of the kingfisher bird genus' in English Halcyon. It is also speculated that Alkyóne is derived from alké (ἀλκή, "prowess, battle, guard") and onéo (ὀνέω, from ὀνίνεμι, onínemi, "to help, to please").