The extent of the connection between Indo-Iranian Mitra/Mithra and Roman Mithras has been vehemently debated for the last thirty years. One of the several problems in outlining the history of Mit(h)ra(s) has been the definition of the Iranian Mithra. In particular, the process by which he becomes a solar deity in the postAvestan period needs clarification. This study considers the history of Mithra with regard to solar mythology; it describes a set of myths from the traditions of two neighbors to Iran — Greece and India. In this set of myths, the Sun is the guardian of contracts and cattle; the ritual of sacrifice relates these two wards, as cattle are victims in the ritual, which may be understood as a contract between gods and humans. With this mythic system recovered from the oldest Greek and Indic texts, the history of Iranian Mithra is reviewed with the intent of interpreting that god: he has assumed the role typically assigned to the Sun in a similar mythic complex. Themes in the myth and cult of Roman Mithras are suggested for comparison.