In ancient Greek religion and mythology, Demeter (/dɪˈmiːtər/; Attic: Δημήτηρ Dēmḗtēr [dɛːmɛ́ːtɛːr]; Doric: Δαμάτηρ Dāmā́tēr) is the Olympian goddess of the harvest and agriculture, presiding over grains and the fertility of the earth. She was also called Deo (Δηώ).. Her cult titles include Sito (Σιτώ), "she of the Grain", as the giver of food or grain, and Thesmophoros (θεσμός, thesmos: divine order, unwritten law; φόρος, phoros: bringer, bearer), "giver of customs" and/or "legislator", in association with the secret female-only festival called the Thesmophoria.

Though Demeter is often described simply as the goddess of the harvest, she presided also over the sacred law, and the cycle of life and death. She and her daughter Persephone were the central figures of the Eleusinian Mysteries, a religious tradition that predated the Olympian pantheon, and which may have its roots in the Mycenaean period c. 1400–1200 BC. Demeter was often considered to be the same figure as the Anatolian goddess Cybele, and she was identified with the Roman goddess Ceres.