Semus of Delos was a Hellenistic grammarian and antiquarian, active in the 3rd or 2nd century BCE. The Byzantine Suda identifies him as a Peripatetic, though the relevance of this label is unclear. His scholarship focused on local history, religious rituals, and cultural origins, particularly concerning his native Delos.

His major work was the Delias, a multi-volume treatise on Delian antiquities, myths, temple histories, and customs. He also authored specialized studies On Pacans and On Islands. Semus exemplifies Hellenistic antiquarian scholarship. His meticulously researched works, though now fragmentary, became valuable sources for later compilers like Athenaeus, preserving unique evidence for Greek local history, religion, and music.