Iranian philosophy or Persian philosophy can be traced back as far as to Old Iranian philosophical traditions and thoughts which originated in ancient Indo-Iranian roots and were considerably influenced by Zarathustra's teachings. According to the Oxford Dictionary of Philosophy (page 409), the choronology of the subject and science of philosophy starts with the Indo-Iranians, dating this event to 1500 BC. Oxford dictionary also states, "Zarathushtra's philosophy entered to influence Western tradition through Judaism, and therefore on Middle Platonism."
Throughout Iranian history and due to remarkable political and social changes such as the Arab and Mongol invasions of Persia, a wide spectrum of schools of thoughts showed a variety of views on philosophical questions extending from Old Iranian and mainly Zoroastrianism-related traditions, to schools appearing in the late pre-Islamic era such as Manicheism and Mazdakism as well as various post-Islamic schools. Iranian philosophy after Arab invasion of Persia, is characterized by different interactions with the Old Iranian philosophy, the Greek philosophy and with the development of Islamic philosophy. The Illumination School and the Transcendent Philosophy are regarded as two of the main philosophical traditions of that era in Persia.
The teachings of Zarathustra (Zoroaster) appeared in Persia at some point during the period 1700-1800 BCE. His wisdom became the basis of the religion Zoroastrianism, and generally influenced the development of the Iranian branch of Indo-Iranian philosophy. Zarathustra was the first who treated the problem of evil in philosophical terms. He is also believed to be one of the oldest monotheists in the history of religion. He espoused an ethical philosophy based on the primacy of good thoughts (pendar-e-nik), good words (goftar-e-nik), and good deeds (kerdar-e-nik).
The works of Zoroaster and Zoroastrianism had a significant influence on Greek philosophy and Roman philosophy. Several ancient Greek writers such as Eudoxus of Cnidus and Latin writers such as Pliny the Elder praised Zoroastrian philosophy as "the most famous and most useful". Plato learnt of Zoroastrian philosophy through Eudoxus and incorporated much of it into his own Platonic realism. In the 3rd century BC, however, Colotes accused Plato's The Republic of plagiarizing parts of Zoroaster's On Nature, such as the Myth of Er.
Zarathustra was known as a sage, magician and miracle-worker in post-Classical Western culture, though almost nothing was known of his ideas until the late eighteenth century. By this time his name was associated with lost ancient wisdom and was appropriated by Freemasons and other groups who claimed access to such knowledge. He appears in Mozart's opera "Die Zauberflöte" under the variant name "Sarastro", who represents moral order in opposition to the "Queen of the Night". Enlightenment writers such as Voltaire promoted research into Zoroastrianism in the belief that it was a form of rational Deism, preferable to Christianity.
In 2005, the Oxford Dictionary of Philosophy ranked Zarathustra number two in the chronology of philosophical events. Zarathustra's impact lingers today due in part to the system of rational ethics he founded called Mazda-Yasna. The word Mazda-Yasna is avestan and is translated as "Worship of Wisdom" in English.
Throughout Iranian history, due to Greek and Arabic influence, a wide spectrum of schools of thoughts showed a variety of views on philosophical questions extending from Old Iranian and Zoroastrian traditions, to schools appearing in the late pre-Islamic era, to various Islamic schools. Iranian philosophy after the Arab conquest of Persia is characterized by different interactions with the Old Iranian philosophy with Greek and Islamic philosophy. The Illumination School and the Transcendent Philosophy are regarded as two of the main philosophical traditions of that era in Persia. Zoroastrianism likely had as much influence on the formation of Christianity as did Judaism and the Greek mystery religions.
Manichaeism, founded by Mani, was influential from North Africa in the West, to China in the East. Its influence subtly continues in Western Christian thought via Saint Augustine of Hippo, who converted to Christianity from Manichaaeism, which he passionately denounced in his writings, and whose writings continue to be influential among Catholic, Protestant, and Orthodox theologians. An important principle of Manichaeism was its dualistic cosmology/theology, which it shared with Mazdakism, a philosophy founded by Mazdak. Under this dualism, there were two original principles of the universe: Light, the good one; and Darkness, the evil one. These two had been mixed by a cosmic accident, and man's role in this life was through good conduct to release the parts of himself that belonged to Light. Mani saw the mixture of good and bad as a cosmic tragedy, while Mazdak viewed this in a more neutral, even optimistic way.
Mazdak (d. 524/528 CE) was a proto-socialist Persian reformer who gained influence under the reign of the Sassanian king Kavadh I. He claimed to be a prophet of God, and instituted communal possessions and social welfare programs.
The Intellectual Tradition in Persia continued after Islam and has had much effects on Iranian Philosophy. The main schools for such developments and studies were, and to some extents still are, Shiraz, Khurasan, Maragheh, Isfahan, Tehran.
In the Islamic Golden Age, due to Avicenna's (Ibn Sina's) successful reconciliation between Aristotelianism and Neoplatonism along with Kalam, Avicennism eventually became the leading school of Islamic philosophy by the 12th century. Avicenna had become a central authority on philosophy by then, and several scholars in the 12th century commented on his strong influence at the time:
"People nowadays [believe] that truth is whatever [Ibn Sina] says, that it is inconceivable for him to err, and that whoever contradicts him in anything he says cannot be rational."
Avicennism was also influential in medieval Europe, particularly his doctrines on the nature of the soul and his existence-essence distinction, along with the debates and censure that they raised in scholastic Europe. This was particularly the case in Paris, where Avicennism was later proscribed in 1210. Nevertheless, his psychology and theory of knowledge influenced William of Auvergne and Albertus Magnus, and his metaphysics had an impact on the thought of Thomas Aquinas.
Illuminationist philosophy was a school of Islamic philosophy founded by Shahab al-Din Suhrawardi in the 12th century. This school is a combination of Avicenna’s philosophy and ancient Iranian philosophy, along with many new innovative ideas of Suhrawardi. It is often described as having been influenced by Neoplatonism.
Transcendent Theosophy is the school of Islamic philosophy founded by Mulla Sadra in the 17th century. His philosophy and ontology is considered to be just as important to Islamic philosophy as Martin Heidegger's philosophy later was to Western philosophy in the 20th century. Mulla Sadra bought "a new philosophical insight in dealing with the nature of reality" and created "a major transition from essentialism to existentialism" in Islamic philosophy, several centuries before this occurred in Western philosophy.
Philosophy was and still is a popular subject of study in Iran. Previous to Western style universities, philosophy was a major field of study in religious seminaries. Comparing the number of philosophy books currently published in Iran with that in other countries, Iran possibly ranks first in this field but it is definitely on top in terms of publishing philosophy books. 
Perhaps some of the most notable Iranian philosophers and intellectuals of the twentieth century are: Dariush Shayegan, Morteza Motahhari, Mustafa Malekiyan, Javad Tabatabaei, Hossein Nasr,and Mahmoud Khatami, Ahmad Fardid, Reza Davari, Abdolkarim Soroush, Gholamhusayn Ibrahimi Dinani, Hassan Hasanzadeh Amoli, , javadi amoli. Some of the most notable but late philosophers of contemporary iranian academia are Allameh Hossein tabatbai, Mehdi Haeri Yazdi, Jalaleddin Ashtiani , Kazem assar, Ibrahim Ashtyani, Abolhasan Jelveh, Mohammad Hosayn Gharavi isfahani (kompani), Badkobehie,Mohammad Taghi Jafari, , mohammad tagi amoli,Ruhollah Khomeini . Some famous university professors and scholars of philosophy are: Nasrollah Pourjavady, Gholamreza Aavani, Mohsen Kadivar, and Mohsen Jahangiri, Karim Mojtadedi, Hamid Vahid Dastgerdi.
Among journals being published in Iran on philosophy there are [FALSAFEH-The Iranian Journal of Philosophy] published by the department of philosophy of the University of Tehran since 1972 and Hikmat va Falsafeh published by Allamah Tabataba'i University in Tehran, Ma'rifat-e Falsafeh published by the Imam Khomeini Education and Research Institute in Qom, and many others. Also worthy of mention is the journal, Naqd o Nazar published by Daftar Tablighat in Qom, which often includes articles on philosophical topics and other issues of interest to religious thinkers and intellectuals.
However, it is important to note that Sufism has had a great amount of inluence on Iranian/Persian philosophy.
In the history of Islamic philosophy, there were a few Persian philosophers who had their own schools of philosophy: Avicenna, al-Farabi, Shahab al-Din Suhrawardi and Mulla Sadra. Some philosophers did not offer a new philosophy, rather they had some innovations: Mirdamad, Khajeh Nasir and Qutb al-Din Shirazi belong to this group. Some philosophers had new narration of existing philosophies: Ali Modarres is an example of such philosophers.