Isis, the principal goddess of the Egyptians, the wife of Osiris, and the mother of Horus, with whom she formed the most popular triad in Egyptian mythology. (See Osiris.) She was adored as the great benefactress of Egypt, who had instructed her people in the art of cultivating wheat and barley, which were always carried in her festal processions. In Greece, where her worship was introduced at a very early period, she was occasionally addressed as Pelagia, the queen of the sea. From Greece her worship passed into Italy, and was established in the first century B. C. at Rome, where it became popular. In 43 B. 0. the triumvirs, in order to ingratiate themselves with the people, commanded a temple of Isis and Serapis to be founded, and publicly sanctioned their worship. The principal Roman temple of Isis stood in the Campus Martius, and hence the goddess was often called Isis Campensis. The Romans identified with her a native goddess of the Gauls, Sicilians, and Germans. The priests of Isis wore linen garments, and her votaries in the public processions wore masks representing the heads of dogs.

In works of art she usually appears with the figure and face of Juno, arrayed in a long tunic, wearing a wreath of lotus flowers, and in her right hand a sistrum.