Musaeus or Musaios was the name of three Greek poets.

The first Musaeus was a mythical seer and priest, the pupil or son of Orpheus, and is said to have been the founder of priestly poetry in Attica. According to Pausanias, he was buried on the Museum hill, south-west of the Acropolis. He composed dedicatory and purificatory hymns and prose treatises, and oracular responses. These were collected and arranged in the time of Peisistratus by Onomacritus, who added interpolations. The mystic and oracular verses and customs of Attica, especially of Eleusis, are connected with his name (Herodotus vii. 6; viii. 96; ix. 43). A Titanomachia and Theogonia are also attributed to him by Gottfried Kinkel (Epicorum graecorum fragmenta, 1878).

Herodotus reports that, during the reign of Pisistratus at Athens, the scholar Onomacritus was charged with compiling the oracles of Musaeus, but that he inserted forgeries of his own devising, which were detected by Lasus of Hermione.

The second Musaeus was an Ephesian attached to the court of the kings of Pergamum, who wrote a Perseis, and poems on Eumenes and Attalus (Suidas s.v.).

The third Musaeus (called Grammaticus in all the manuscripts) is of uncertain date, but probably belongs to the beginning of the 6th century, as his style and metre are evidently modelled on those of Nonnus. He must have lived before Agathias (530-582) and has been identified with the friend of Procopius whose poem (340 hexameter lines) on the story of Hero and Leander is by far the most beautiful of the age (editions by Franz Passow, 1810; GH Schafer, 1825; C Dilthey, 1874). The little love-poem Alpheus and Arethusa (Anthol. pal. ix. 362) is also ascribed to Musaeus.