Question: The Prime Minister of Iran was a political post in Iran that had existed during several different periods of time starting with the Qajar era (when the country was internationally known as Persia) until its most recent revival from 1979 to 1989 following which 1979 events involving the overthrow of the Pahlavi dynasty under Mohammad Reza Shah Pahlavi, who was supported by the United States, and eventual replacement of 2500 years of Iranian monarchy with an Islamic Republic regime?
Context: In the Western world, Persia (or one of its cognates) was historically the common name for Iran.  In 1935, Reza Shah Pahlavi asked foreign delegates to use the term Iran, the historical name of the country, used by its native people, in formal correspondence.  Iran literally means "Land of Aryans" in Persian language.  Since then, in the Western World, the use of the word "Iran" has become more common.  This also changed the usage of the terms for Iranian nationality, and the common adjective for citizens of Iran changed from Persian to Iranian.  In 1959, the government of Mohammad Reza Shah Pahlavi, Reza Shah Pahlavi's son, announced that both "Persia" and "Iran" could officially be used interchangeably. Sayyed Hasan Taqizādeh (Persian: سید حسن تقی‌زاده‎ ‎ ; September 27, 1878 in Tabriz, Iran – January 28, 1970, in Tehran, Iran) was an influential Iranian politician and diplomat, of Azeri origin, during the Qajar dynasty under the reign of Mohammad Ali Shah, as well as the Pahlavi dynasty under the reign of Reza Shah and Mohammad Reza Shah.  Although in the modern political history Taqizadeh is known as a secular politician, who believed that "outwardly and inwardly, in body and in spirit, Iran must become Europeanized", he came from a traditional Islamic Sayyed-family (descendant of Muhammad).  His father, Sayyed Taqi, was a clergyman and when Sayyed Hasan became a mullah, it seemed likely that he would follow in his father's footsteps.  From an early age Taqizadeh showed interest in enlightened ideas and the Western concept of constitutionalism.  This interest can be traced back to the socio-political sphere in which Taqizadeh became an adult.  He grew up in Tabriz, the capital city of East Azerbaijan province, which was the gateway to the modern and progressive ideas coming from Russia and especially Western Europe.  In the time of World War I, World War II and after, Taqizadeh was the most influential person in Iran who support intress of German Empire against Russia and Britain. The Pahlavi dynasty (Persian: دودمان پهلوی‎ ‎ ) was the ruling house of Imperial State of Iran from 1925 until 1979, when the monarchy was overthrown and abolished as a result of the Iranian Revolution.  The dynasty was founded by Reza Shah Pahlavi in 1925, a former Brigadier-General of the Persian Cossack Brigade, whose reign lasted until 1941 when he was forced to abdicate by the Allies after the Anglo-Soviet invasion.  He was succeeded by his son, Mohammad Reza Shah Pahlavi, the last Shah of Iran. The demonstrations of June 5 and 6, also called the events of June 1963 or (using the Iranian calendar) the 15 Khordad uprising (Persian: قیام پانزده خرداد‎ ‎ ), were protests in Iran against the arrest of Ayatollah Ruhollah Khomeini after his denouncement of Iranian Shah Mohammad Reza Pahlavi and Israel.  The Shah's regime was taken by surprise by the massive public demonstrations of support, and although these were crushed within days by the police and military, the events established the importance and power of (Shia) religious opposition to the Shah, and Khomeini as a major political and religious leader.  Fifteen years later, Khomeini was to lead the Iranian Revolution which overthrew the Shah and his Pahlavi dynasty and established the Islamic Republic of Iran. Sayyid Ruhollah Mūsavi Khomeini (Persian: سید روح‌الله موسوی خمینی‎ ‎ ] ; 24 September 1902 – 3 June 1989), known in the Western world as Ayatollah Khomeini, was an Iranian Shia Muslim religious leader, philosopher, revolutionary, and politician.  He was the founder of the Islamic Republic of Iran and the leader of the 1979 Iranian Revolution that saw the overthrow of the 2500 years of Persian monarchy and Mohammad Reza Pahlavi, the last Shah of Iran.  Following the revolution, Khomeini became the country's Supreme Leader, a position created in the constitution of the Islamic Republic as the highest-ranking political and religious authority of the nation, which he held until his death.  He was succeeded by Ali Khamenei on 4 June 1989. The Iranian Revolution (Persian: انقلاب ایران‎ , "Enqelāb-e Iran " ‎ ; also known as the Islamic Revolution or the 1979 Revolution;) refers to events involving the overthrow of the Pahlavi dynasty under Mohammad Reza Shah Pahlavi, who was supported by the United States, and eventual replacement of 2500 years of Iranian monarchy with an Islamic Republic regime under the Grand Ayatollah Ruhollah Khomeini, the leader of the revolution, supported by various leftist and Islamist organizations and student movements. The Prime Minister of Iran was a political post in Iran that had existed during several different periods of time starting with the Qajar era (when the country was internationally known as Persia) until its most recent revival from 1979 to 1989 following the Iranian Revolution. Mohammad Reza Pahlavi (Persian: محمدرضا پهلوی‎ , "Mohammad Rezā Pahlavi " ‎ , ] ; 26 October 1919 – 27 July 1980), known as Mohammad Reza Shah (Persian: محمدرضا شاه‎ , "Mohammad Rezā Šāh " ‎ ), was the Shah of Iran from 16 September 1941 until his overthrow by the Iranian Revolution on 11 February 1979.  Mohammad Reza Shah took the title Shāhanshāh ("Emperor" or "King of Kings") on 26 October 1967.  He was the second and last monarch of the House of Pahlavi of the Iranian monarchy.  Mohammad Reza Shah Pahlavi held several other titles, including that of Āryāmehr (Light of the Aryans) and Bozorg Arteshtārān (Head of the Warriors).  His dream of the Great Civilization in Iran led to a rapid industrial and military expansion as well as economic and social reforms. The Imperial state of Iran, the government of Iran during the Pahlavi dynasty, lasted from 1925 to 1979.  During that time two monarchs — Reza Shah Pahlavi and his son Mohammad Reza Shah Pahlavi — employed secret police, torture, and executions to stifle political dissent.  The Pahlavi dynasty has sometimes been described as a "royal dictatorship", or "one man rule". An Enduring Love: My Life with the Shah (ISBN  ) is a book written in 2004 by Farah Pahlavi, the former Shahbanu (Empress) of Iran, who has been living in exile since the Iranian Revolution in 1979 which saw overthrow of the Pahlavi Dynasty.  It is a memoir about Farah, her life before she met the Shah and how she married him and became the Queen and later Empress of Iran.  The book is also about her husband, Mohammad Reza Shah Pahlavi, his personality, his family and how he reigned over the country of Iran for 37 years.
Answer: Iranian Revolution