Anti-Iranian sentiment, also known as Anti-Persian sentiment, Persophobia, or Iranophobia refers to feelings and expression of hostility, hatred, discrimination, or prejudice towards Iran (historically known as Persia in the Western world) and its culture, and towards persons based on their association with Iran and Iranian culture. Its opposite is Persophilia.
The word "ʻajam" is derived from the root ʻ-J-M and refers to "unclear, vague and/or incomprehensible " as opposed to "ʻarabi", which means "clear, understandable; with perfect Arabic tongue". ʻAjam came to mean "one who mumbles" (کند زبانان), similar to the Slavicethnonym and their usage of "mutes" to refer to Germans. It came to be "applied especially to Persians", and the distinction of the two terms is found already in pre- and early Islamic literature (ʻAjam Temtemī). "In general, ajam was a pejorative term, used by Arabs because of their contrived social and political superiority in early Islam.", as summarized by Clifford Bosworth. Although Arabicdictionaries state that the word ʻajami is used for all non-Arabs, the designation was primarily used for Persians.
Sunni Arabs use slurs against Persians by calling them "fire worshippers" and "majoos", "majus" (ماجوس) which means Zoroastrians, Magi.
Anti-Iranianism in early Islamic period
Patrick Clawson states that "The Iranians chafed under Umayyad rule. The Umayyads rose from traditional Arab aristocracy. They tended to marry other Arabs, creating an ethnic stratification that discriminated against Iranians. Even as Arabs adopted traditional Iranian bureaucracy, Arab tribalism disadvantaged Iranians."
Many Arab Muslims believed that Iranian converts should not clothe themselves as Arabs, among many other forms discrimination that existed.Mu'awiyah, in a famous letter addressed to Ziyad ibn Abih, the then governor of Iraq, wrote:
Be watchful of Iranian Muslims and never treat them as equals of Arabs. Arabs have a right to take in marriage their women, but they have no right to marry Arab women. Arabs are entitled to inherit their legacy, but they cannot inherit from an Arab. As far as possible they are to be given lesser pensions and lowly jobs. In the presence of an Arab, a non-Arab shall not lead the congregation prayer, nor they are to be allowed to stand in the first row of prayer, nor to be entrusted with the job of guarding the frontiers or the post of a qadi.
Mistreatment of Iranians and other non-Arabs during the early period of Islam is well documented. Under the rule of Umayyads, although many of the mawlas (non-Arab Muslims) employed by a patron enjoyed favourable position as equal to an Arab Muslim, they were generally victims of cultural bias and even sometimes considered to be of an equal footing of a slave. They often were victims of what surmounts as cultural genocide (burning of Books, prohibition of language and Iran's many belief systems). According to sources of that time, the mistreatment of mawlas was a general rule. They were denied any positions in the government under Umayyad rule.
The Umayyid Arabs are even reported to have prevented the mawali from having kunyahs, as an Arab was only considered worthy of a kunya. They were required to pay taxes for not being an Arab:
During the early centuries of Islam when the Islamic empire was really an Arab kingdom, the Iranians, Central Asians and other non-Arab peoples who had converted to Islam in growing numbers as mawali or 'clients' of an Arab lord or clan, had in practice acquired an inferior socio-economic and racial status compared to Arab Muslims, though the mawali themselves fared better than the empire's non-Muslim subjects, the Ahl al-Dhimmah ('people of the covenant'). The ةawali, for instance, paid special taxes, often similar to the jizyaا (poll tax) and the kharaj (land tax) levied on the Zoroastrians and other non-Muslim subjects, taxes which were never paid by the Arab Muslims.
After the Islamic conquest of the Sassanid Empire, during the reign of the Ummayad dynasty, the Arab conquerors imposed Arabic as the primary language of the subject peoples throughout their empire. In an effort of vultural genocide, and unhappy with the prevalence of the Iranian languages in the divan, Hajjāj ibn Yusuf ordered the official language of the conquered lands to be replaced by Arabic, often by force. According to Biruni
When Qutaibah bin Muslim under the command of Al-Hajjaj bin Yousef was sent to Khwarazmia with a military expedition and conquered it for the second time, he swiftly killed whomever wrote the Khwarazmian native language that knew of the Khwarazmian history, science and culture. He then killed all their Zoroastrian priests and burned and wasted their books, until gradually the illiterate only remained, who knew nothing of writing and hence their history was mostly forgotten.
— Biruni From The Remaining Signs of Past Centuries, 
It is difficult to imagine the Arabs not implementing anti-Persian policies in light of such events, writes Zarrinkoub in his famous Two Centuries of Silence, where he exclusively writes of this topic. Reports of Persian speakers being tortured and killed are also given in al-Aghānī.
Predominantly Shia Islamic Iran has always exhibited a sympathetic side for Ali (the cousin and son-in-law of Muhammad) and his progeny. Even when Persia was largely Sunni, this was still evident as can be seen from the writings remaining from that era. Rumi for example praises Ali in a section entitled "Learn from ʻAli". It recounts Ali's explanation as to why he declined to kill someone who had spit in his face as ʻAli was defeating him in battle. Persian literature in praise of Ali's progeny is quite ubiquitous and abundant. These all stem from numerous traditions regarding Ali's favor of Persians being as equals to Arabs.
Several early Shiite sources speak of a dispute arising between an Arab and an Iranian woman. Referring the case to ʻAli for arbitration, ʻAli reportedly did not allow any discrimination between the two to take place. His judgment thus invited the protest of the Arab woman. Thereupon, ʻAli replied, "In the Qurʼan, I did not find the progeny of Ishmael (the Arabs) to be any higher than the Iranians."
In another such tradition, Ali was once reciting a sermon in the city of Kufah, when
Ash'as ibn Qays, a commander in the Arab army protested, "Amir-al-Momeneen! These Iranians are excelling the Arabs right in front of your eyes and you are doing nothing about it!" He then roared, "I will show them who the Arabs are!" Ali immediately retorted, "While fat Arabs rest in soft beds, the Iranians work hard on the hottest days to please God with their efforts. And what do these Arabs want from me? To ostracize the Iranians and become an oppressor! I swear by the God that splits the nucleus and creates Man, I heard the prophet once say, just as you strike the Iranians with your swords in the name of Islam, so will the Iranians one day strike you back the same way for Islam."
When the Sassanid city of Anbar fell to the forces of Mu'awiyeh, news reached Ali that the city had been sacked and plundered spilling much innocent blood. Early Shi'ite sources report that Ali gathered all the people of Kufa to the mosque and gave a fiery sermon. After describing the massacre, he said, "If somebody hearing this news now faints and dies of grief, I fully approve of it!" It is from here that Ali is said to have had more sympathy for Iranians while author S. Nureddin Abtahi claims that Umar highly resented them. However, a hadith on Ali's banning of the game of shatranj (chess), narrates that Ali said "Chess is the gambling game of the Ajam"
Sati' al-Husri's campaigns against schools suspected of being positive towards Persia are well documented. One dramatic example is found in the 1920s when the Iraqi Ministry of Education ordered Husri to appoint Muhammad Al-Jawahiri as a teacher in a Baghdad school. A short excerpt of Husri's interview with the teacher is revealing:
"Husri: First, I want to know your nationality.
Jawahiri: I am an Iranian.
Husri: In that case we cannot appoint you."
Saddam Hussein Abd al-Majid al-Tikriti forced out tens of thousands of people of Persian origin from Iraq in the 1970s, after having been accused of being spies for Iran and Israel. Today, many of them live in Iran.
Early on in his career, Saddam Hussein and pan-Arab ideologues targeted the Arabs of southwest Iran in an endeavor to have them separate and join 'the Arab nation.' When this failed, they attacked and killed a large number of this population.  Hussein made no effort to conceal Arab nationalism in his war against Iran (which he called "the second Battle of al-Qādisiyyah). An intense campaign of propaganda during his reign meant that many school children were taught that Iran provoked Iraq into invading and that the invasion was fully justified.
"Yellow revolution", "yellow wind", "yellow storm" were Oriental-Phobic slurs used by Saddam Hussein against Iran due to Hulagu's 1258 sack of Baghdad during the Mongol wars and the terms "Persian" and "Elamites" were also used by Saddam as insults.
"In your name, brothers, and on behalf of the Iraqis and Arabs everywhere, we tell those [Persian] cowards who try to avenge Al-Qadisiyah that the spirit of Al-Qadisiyah as well as the blood and honor of the people of Al-Qadisiyah who carried the message on their spearheads are greater than their attempts."
In the war, Iraq made extensive use of chemical weapons (such as mustard gas) against Iranian troops and civilians as well as Iraqi Kurds. Iran expected a condemnation by UN of this act and sent allegation to UN. At time (-1985) the UN Security Council issued statements that "chemical weapons had been used in the war." However, in these UN-statements Iraq was not mentioned by name, so that the situation is viewed as "in a way, the international community remained silent as Iraq used weapons of mass destruction against Iranian as well as Iraqi Kurds" and it is believed that the United States had prevented UN from condemning Iraq.
In December 2006, Hussein said he would take responsibility "with honour" for any attacks on Iran using conventional or chemical weapons during the 1980–1988 war, but he took issue with charges he ordered attacks on Iraqis.
On the execution day, Hussein said, "I spent my whole life fighting the infidels and the intruders, [...] I destroyed the invaders and the Persians." He also stressed that the Iraqis should fight the Americans and the Persians. Mowaffak al Rubiae, Iraq's National Security adviser, who was a witness to Hussein's execution described him as repeatedly shouting "down with Persians." Hussein built an anti-Iranian monument called Hands of Victory in Baghdad in 1989 to commemorate his declaration of victory over Iran in the Iran-Iraq war (though the war is generally considered a stalemate). After his fall, it was reported that the new Iraqi government had organized the Committee for Removing Symbols of the Saddam Era and that the Hands of Victory monument had begun to be dismantled. However, the demolition was later halted.