A seraph (pl. seraphim ( /ˈsɛr.ə.fɪm/); Hebrew: שְׂרָפִים śərāfîm, singular שָׂרָף śārāf; Latin: seraphi[m], singular seraph[us]; Greek: σεραφείμ) is a type of celestial or heavenly being in the Abrahamic religions.

Literally "burning ones", the word seraph is normally a synonym for serpents when used in the Hebrew Bible. A seminal passage in the Book of Isaiah (6.1-8) used the term to describe fiery six-winged beings that fly around God's throne singing "holy, holy, holy". This throne scene, with its triple invocation of holiness (a formula that came to be known as the trisagion), profoundly influenced subsequent theology, literature and art. Its influence is frequently seen in works depicting angels, heaven and apotheosis. Seraphs are mentioned as celestial beings in an influential Hellenistic work, the Book of Enoch, and the Book of Revelation. Tradition places seraphs in the fifth rank of ten in the Jewish angelic hierarchy and the highest rank in the Christian angelic hierarchy.

The word seraphim, literally "burning ones", transliterates a Hebrew plural noun; translation yields seraphs. The singular, "seraph", is more properly rendered sarap. The word sarap/seraphim appears three times in the Torah (Numbers 21:6-8, Deuteronomy 8:15) and four times in the Book of Isaiah (6:2-6, 14:29, 30:6). In Numbers and Deuteronomy the "seraphim" are serpents – the association of serpents as "burning ones" is possibly due to the burning sensation of the poison. Isaiah also uses the word in close association with words to describe snakes (nahash, the generic word for snakes, in 14:29, and efeh, viper, in 30:6).