Cult of Asclepius

Founded in the 4th century, B.C.E., the cult of Asclepius was named for the ancient Greek god of medicine and healing.  Asclepian priests ran healing centers that offered dream therapy for the sick.  Patients would spend a night in the temple, praying for a dream of the god.  In the morning, the priests would interpret the dream and recommend treatment.  The cult continued during Roman rule until the rise of Christianity in the late 5th century.  Asclepius was eventually assimilated into the cult of the saints, some of whom were considered dream healers.

Sources:

Miller, Dreams in Late Antiquity
Encyclopedia Mythica, “Asclepius”