Lucifer of Cagliari, d. 370, bishop of Cagliari, Sardinia (353-70), violent opponent of Arianism. As legate of Pope Liberius he went to the council at Milan (355) that Constantius disbanded by exiling the Catholic delegates. Lucifer was bitter against those who seemed to submit to Arianism, and on his return to Sardinia (362) he formed a sect of his own, barring all who had strayed into Arianism at all. His peremptory consecration of a bishop for Antioch (outside his jurisdiction) perpetuated the schism of Meletius.

Lucifer [Lat.,=light-bearing], in Christian tradition a name for Satan. In the Vulgate, Lucifer served as a translation of the Hebrew epithet meaning "Day Star," a name associated with the presumptuous King of Babylon in the Book of Isaiah. Some early Christian writers found a parallel in the Gospel of St. Luke, where Jesus refers to Satan falling like lightning from heaven. On this basis they identified Isaiah's "Day Star" with Satan and concluded that there was scriptural authority for designating him "light-bearer." In antiquity Lucifer was also the name given Venus as the morning star.

In classical mythology, the morning star (the planet Venus at dawn), personified as a male figure. Lucifer (Latin: “Light-Bearer”) carried a torch and served as herald of the dawn. In Christian times, Lucifer came to be regarded as the name of Satan before his fall; it was thus used by John Milton in Paradise Lost.

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