Valerios Stais (; b. Kythira 1857 – d. Athens 1923) was a Greek archaeologist. He was born in Kythera. He studied medicine and later archaeology. He became the director of the National Archaeological Museum of Athens in 1887 and held that post until his death. During that period he organized or participated in excavations in Epidaurus, Argolis, Attica, Dimini, Antikythera and elsewhere. He also wrote a lot of archaeological studies, published in various papers and mainly in Archeologiki Efimeris (Αρχαιολογική Εφημερίς "Archaeological Newspaper") http://www.archetai.gr/site/content.php?artid=1464, and many books.

Valerios Stais also became the discoverer of the Antikythera mechanism.