The name Mithras (Latin, equivalent to Greek "Μίθρας",) is a form of Mithra, the name of an Iranian god, a point acknowledged by Mithras scholars since the days of Franz Cumont. The Greek form of the name appears in Xenophon's biography of Cyrus, the Cyropaedia, a work written in the fourth century BC.
The word Mithra occurs as the name of a praiseworthy being in the Zoroastrian text, the Zend Avesta. Similar deity names in related Indo-european languages include Mitra, "मित्रः" found in Rig Vedic hymns. In Sanskrit, "mitra" means "friend" or "friendship".
In the inscribed peace treaty of c. 1400 BC between Hittites and the Hurrian kingdom of the Mitanni in the area southeast of Lake Van in Armenian Highlands, the form mi-it-ra- appears as the name of a god invoked together with four other divinities as witnesses and keepers of the pact. Robert Turcan describes this inscription as "the earliest evidence of Mithras in Asia Minor".
The exact form of a Latin or classical Greek word varies due to the grammatical process of declension. There is archeological evidence that in Latin worshippers wrote the nominative form of the god's name as "Mithras". However, in Porphyry's Greek text De Abstinentia (Περὶ αποχης εμψγχων), there is a reference to the now-lost histories of the Mithraic mysteries by Euboulus and Pallas, the wording of which suggests that these authors treated the name "Mithra" as an indeclinable foreign word.
In later antiquity, the Greek name of Mithras (Μίθραϲ) occurs in the text known as the Mithras Liturgy, part of the Paris Great Magical Papyrus (Paris Bibliothèque Nationale Suppl. gr. 574); here Mithras is given the epithet "the great god", and is identified with the sun god Helios. There have been different views among scholars as to whether this text is an expression of Mithraism as such. Franz Cumont argued that it isn't; Marvin Meyer thinks it is; while Hans Dieter Betz sees it as a synthesis of Greek, Egyptian, and Mithraic traditions.
The Persian associations of the name Mithras are acknowledged by scholars such as David Ulansey who interpret Roman Mithraism as something new. A scenario discussed by Ulansey is that "the Roman cult of Mithras was actually a new religion" which "borrowed the name of an Iranian god in order to give itself an exotic oriental flavor".
According to another historian of Mithraism, John R. Hinnells: "The god is unique in being worshipped in four distinct religions: Hinduism (as Mitra), in Iranian Zoroastrianism and Manicheism (as Mithra), and in the Roman Empire (as Mithras)."  Mary Boyce, a researcher of ancient Iranian religions, writes that even though Roman Empire Mithraism seems have had less Iranian content than historians used to think, still "as the name Mithras alone shows, this content was of some importance." 
- Charlton T. Lewis, Charles Short. A Latin Dictionary
- Ulansey, David (1991). Origins of the Mithraic Mysteries. New York: Oxford UP. p. 90. ISBN 0-19-506788-6.
It is therefore highly likely that it was in the context of Mithridates' alliance with the Cilician pirates that there arose the synchretistic link between Perseus and Mithra which led to the name Mithras (a Greek form of the name Mithra) being given to the god of the new cult.
- Ulansey, David (1991). Origins of the Mithraic Mysteries. New York: Oxford UP. p. 8. ISBN 0-19-506788-6.
Cumont's... argument was straightforward and may be summarized succinctly: the name of the god of the cult, Mithras, is the Latin (and Greek) form of the name of an ancient Iranian god, Mithra; in addition, the Romans believed that their cult was connected with Persia (as the Romans called Iran); therefore we may assume that Roman Mithraism is nothing other than the Iranian cult of Mithra transplanted into the Roman Empire.
- Xenophon, Cyropaedia 7.5.53. Cited in Henry George Liddell and Robert Scott, A Greek-English Lexicon
- E.g. in Avesta: Yasna: 1:3 Avesta: Yasna: 1:11
- Ware writes that the Romans borrowed the name "Mithras" from Avestan Mithra.Ware, James R.; Kent, Roland G. (1924). "The Old Persian Cuneiform Inscriptions of Artaxerxes II and Artaxerxes III". Transactions and Proceedings of the American Philological Association. 55: 52–61. doi:10.2307/283007. JSTOR 283007. pp. 52–61.
- E.g. in Rig Veda 3, Hymn 59
- Michael Speidel (1980). Mithras-Orion: Greek hero and Roman army god. Brill. p. 1. ISBN 978-90-04-06055-5.
India's sacred literature refers to him since the hymns of the Rig Veda. But it was in Iran where Mithras rose to the greatest prominence: rebounding after the reforms of Zarathustra, Mithras became one of the great gods of the Achaemenian emperors and to this very day he is worshipped in India and Iran by Parsees and Zarathustrians.
- Hopfe, Lewis M.; Richardson, Henry Neil (September 1994). "Archaeological Indications on the Origins of Roman Mithraism". In Lewis M. Hopfe (ed.). Uncovering ancient stones: essays in memory of H. Neil Richardson. Eisenbrauns. p. 150. ISBN 978-0-931464-73-7. Retrieved 19 March 2011.
All theories of the origin of Mithraism acknowledge a connection, however vague, to the Mithra/Mitra figure of ancient Aryan religion.CS1 maint: discouraged parameter (link)
- Turcan, Robert (1996). The cults of the Roman Empire. Wiley-Blackwell. pp. 196–. ISBN 978-0-631-20047-5. Retrieved 19 March 2011.
The name Mithras comes from a root mei- (which implies the idea of exchange), accompanied by an instrumental suffix. It was therefore a means of exchange, the 'contract' which rules human relations and is the basis of social life. In Sanskrit, mitra means 'friend' or 'friendship', like mihr in Persian. In Zend, mithra means precisely the 'contract', which eventually became deified following the same procedure as Venus, the 'charm' for the Romans. We find him invoked with Varuna in an agreement concluded c. 1380 BC between the king of the Hittites, Subbiluliuma, and the king of Mitanni, Mativaza....It is the earliest evidence of Mithras in Asia Minor.CS1 maint: discouraged parameter (link)
- Thieme, Paul (1960), "The 'Aryan' Gods of the Mitanni Treaties", Journal of the American Oriental Society, 80 (4). pp. 301-317.
- "Mithraism". Encyclopædia Britannica Online. Encyclopædia Britannica. Retrieved 2011-04-19.
First of all, he was the god of contract and mutual obligation. In a cuneiform tablet of the 15th century bc that contains a treaty between the Hittites and the Mitanni, Mithra is invoked as the god of oath. Furthermore, in some Indian Vedic texts the god Mitra (the Indian form of Mithra) appears both as “friend” and as “contract.” ...In short, Mithra may signify any kind of communication between men and whatever establishes good relations between them.CS1 maint: discouraged parameter (link)
- Gordon, Richard L. (1978). "The date and significance of CIMRM 593 (British Museum, Townley Collection". Journal of Mithraic Studies II: 148–174.. p. 160: "The usual western nominative form of Mithras' name in the mysteries ended in -s, as we can see from the one authentic dedication in the nominative, recut over a dedication to Sarapis (463, Terme de Caracalla), and from occasional grammatical errors such as deo inviato Metras (1443). But it is probable that Euboulus and Pallas at least used the name Mithra as an indeclinable (ap. Porphyry, De abstinentia II.56 and IV.16)."
- Meyer, Marvin (2006). "The Mithras Liturgy". In A.J. Levine; Dale C. Allison, Jr.; John Dominic Crossan (eds.). The historical Jesus in context. New Jersey: Princeton University Press. p. 180. ISBN 0-691-00991-0. (The reference is at line 482 of the Great Magical Papyrus of Paris. The Mithras Liturgy comprises lines 475 - 834 of the Papyrus.)
- See the Greek text with German translation in Albrecht Dieterich, Eine Mithrasliturgie, 2nd edition, pp 1-2
- The "Mithras Liturgy":Text, Translation and Commentary (Tubingen: Mohr Siebeck, 2003). p.12
- Meyer, Marvin (2006). "The Mithras Liturgy". In A.J. Levine; Dale C. Allison, Jr.; John Dominic Crossan (eds.). The historical Jesus in context. New Jersey: Princeton University Press. pp. 180–182. ISBN 0-691-00991-0.
- The "Mithras Liturgy": Text, Translation and Commentary (Tubingen: Mohr Siebeck, 2003)
- Richard Gordon, "Probably Not Mithras", The Classical Review Vol. 55, No. 1 (March 2005), pp. 99-100.
- Ulansey, David. "The Cosmic Mysteries of Mithras". Retrieved 2011-03-30.
However, in 1971 the First International Congress of Mithraic Studies was held in Manchester England... Was it not possible, scholars at the Congress asked, that the Roman cult of Mithras was actually a new religion, and had simply borrowed the name of an Iranian god in order to give itself an exotic oriental flavor?CS1 maint: discouraged parameter (link)
- Hinnells, John R. (1990), "Introduction: the questions asked and to be asked", in Hinnells, John R. (ed.), Studies in Mithraism, Rome: L'Erma di Bretschneider, p. 11
- Boyce, Mary; Grenet, Frantz (1975). Zoroastrianism under Macedonian and Roman rule, Part 1. Brill. pp. 468, 469. ISBN 90-04-09271-4. Retrieved 2011-03-16.
The theory that the complex iconography of the characteristic monuments (of which the oldest belong to the second century A.C.) could be interpreted by direct reference to Iranian religion is now widely rejected; and recent studies have tended greatly to reduce what appears to be the actual Iranian content of this "self consciously 'Persian' religion", at least in the form which it attained under the Roman empire. Nevertheless, as the name Mithras alone shows, this content was of some importance; and the Persian affiliation of the Mysteries is acknowledged in the earliest literary reference to them.CS1 maint: discouraged parameter (link)