The monarchs of Iran ruled for over two and a half millennia, beginning as early as the 8th century BC and enduring until the 20th century AD. The earliest Iranian monarch is generally considered to have been either Deioces of the Median dynasty (c. 727–550 BC) or Cyrus the Great of the Achaemenid dynasty (550–330 BC). The last Iranian monarch was Mohammad Reza Shah of the Pahlavi dynasty (1925–1979), who was overthrown in the Iranian Revolution. Since then, Iran has been governed by theocratic supreme leaders.
In classical antiquity, Iran reached the peak of its power and prestige under the Achaemenid Empire, which stretched from Egypt and parts of Southeast Europe in the west to the Indus Valley and parts of Central Asia in the east. By 323 BC, the Achaemenid Empire's territories had been conquered by the Macedonian Empire during the Wars of Alexander the Great, bringing Iran into the Hellenistic sphere. In the Wars of the Diadochi, the Seleucid Empire (305–129 BC) assumed control of Iran. Native Iranian rule was revived with the expansion of Parthian Empire (247 BC–224 AD) in the Seleucid–Parthian Wars. The Parthians were succeeded by the Sasanian Empire (224–651), which oversaw a golden age in the history of Iranian civilization and existed until the Arab conquest of Iran.
Medieval Iran alternated between being ruled by large foreign empires and being divided into several smaller kingdoms. Most of the Sasanian lands were annexed by the Rashidun Caliphate (638–661), which was succeeded by the Umayyad Caliphate (661–750) and then by the Abbasid Caliphate (749–861). Under the Abbasids, many Iranian figures took part in shaping the Islamic Golden Age, while also leveraging the decline of Arab power to establish independent dynasties and kingdoms – those including the Saffarids (867–1002), Samanids (875–999), Ziyarids (927–1090/1091) and Buyids (934–1062) – thus allowing their native languages to flourish and reviving Sasanian royal iconography and ideology in what became known as the Iranian Intermezzo. In the 11th century, Iran was conquered by the Seljuk Empire (1038–1194), which was Turkic in origin, but culturally Persianate. Further conquests by entities coming from Central Asia occurred over the course of the next five centuries, most notably including the Turkic Khwarazmian Empire (1097–1220/1221), the Mongol Empire (1220–1259), the post-Mongol Ilkhanate (1256–1335), and the Turco-Mongol Timurid Empire (1370–1458). Most of the Timurid territory in Iran was later conquered by the Qara Qoyunlu (1452–1469), followed by the Aq Qoyunlu (1465–1508), both are Turkic tribal confederations.
The year 1501 is considered the beginning of modern Iranian history, as the Safavid dynasty (1501–1736) rose to power and oversaw the conversion of Iran to Shia Islam, marking the region's largest religious shift since the Arab conquest. The collapse of the Safavids led to an intermediate period of turmoil, with rule of Iran contested between Safavid dynasts as well as the Afghan-origin Hotak dynasty (1722–1729). Nader Shah replaced these with the Afsharid Empire (1736–1796), but after his assassination in 1747, the Afsharids competed with the Zand dynasty (1751–1794) under Karim Khan Zand and his successors for supremacy. Iran was eventually reunified by the Qajar dynasty (1789–1925), which was succeeded by the Pahlavi dynasty of Reza Shah. The Pahlavi dynasty was the last to reign before the Iranian monarchy was abolished in 1979.
Ancient Iran (c. 727 BC–AD 651)
The Median dynasty is traditionally considered to have ruled the earliest Iranian state. Whether the Medes ruled an imperial state or merely a loose tribal confederation is disputed among historians. Median history is reconstructed almost solely through ancient Greek sources (particularly Herodotus) and disregards Near Eastern sources, which are fragmentary and do not support the existence of a unified Median Empire. There is also no material or textual evidence left behind by the supposed empire itself. The chronology and names of the Median kings mainly derives from the work of Herodotus.
No ruling title is securely attested for the Median rulers. They might have used xšāyaθiya xšāyaθiyānām ("King of Kings"), later used by the Achaemenids. Ecbatana was the Median capital.
Achaemenid Empire (550–330 BC)
The Achaemenid dynasty originated as local rulers of Anshan under Median suzerainty. They are attributed various ancestors in later legends, including an eponymous figure called "Achaemenes". The earliest securely historical Achaemenid ruler is Cyrus I, king of Anshan in the second half of the seventh century BC. The Achaemenids united all Persian tribes under Cyrus I's son Cambyses I. Under Cambyses I's son, Cyrus II, the Achaemenids defeated the Medes and established the Achaemenid Empire, the largest ever Iranian state.
The standard title used by Achaemenid rulers in Iran from Cyrus II onwards was xšāyaθiya xšāyaθiyānām, xšāyaθiya dahyūnām (lit. 'King of Kings, King of the Lands'). The royal title varied in other parts of the empire. The Achaemenids had several royal cities, including Pasargadae, Susa, Ecbatana, Babylon, Bactra, and Persepolis.
Alexander's empire (331–305 BC)
The Achaemenid Empire was defeated and conquered by Alexander the Great, king of the ancient Greek kingdom of Macedonia, in 331–329 BC. After Alexander's death in 323 BC, the Wars of the Diadochi broke out between his successors, leading to the rapid disintegration of the empire.
Alexander did not assume the former Achaemenid royal title of 'King of Kings'. His main royal title, appearing on coins intended for his Asian territories, was instead basileus (lit. 'king'). To mark his rule over the Achaemenid territories he also sometimes used the new title "Lord of Asia" (sometimes "King of Asia"). The only royal title recorded for Alexander's two immediate heirs is basileus. Alexander ruled his empire from Babylon and planned to establish Babylon and Alexandria in Egypt as the twin imperial capitals. From 319 BC onwards, Alexander's heirs resided in Macedonia while the regency in Asia was contested by several generals.
The main Hellenistic successors of Alexander's empire in Iran were the Seleucids, descendants of the Macedonian general Seleucus I Nicator and the Iranian noblewoman Apama. Seleucus seized most of the east, including Babylonia, in the Wars of the Diadochi and was firmly in control in the region from 312 BC onwards. After Alexander IV's death became public knowledge in 305 BC, Seleucus proclaimed himself king.
The main royal title used by the Seleucids was basileus, as was the case for the other Macedonian successor kingdoms (such as the Ptolemaic Kingdom). Only two Seleucid rulers (Antiochus III, 223–187 BC, and Antiochus VII, 139–129 BC) used the greater megas basileus ('Great King'), the style applied to Achaemenid kings in ancient Greek sources. The Seleucids at first ruled from Seleucia in Mesopotamia, though Antioch was soon made the main capital.
Parthian Empire (c. 250/247 BC–224 AD)
The Arsacids of Parthia, initially Seleucid vassals, originated as leaders of the eastern Iranian Parni tribe in the northeastern steppes. The Parthians gradually challenged Seleucid rule over Iran. Parthian control of Iran was secured through the c. 142 BC conquest of Babylonia. Although fighting continued for years, the death of Antiochus VII Sidetes in 129 BC effectively marked the collapse of the Seleucid Empire, which then lingered on as a rump state in Syria until conquered by the Roman Empire in the 60s BC.
The Parthians presented themselves as heirs of the Achaemenids, though ruled a much more decentralized state. Greek inscriptions were used on Parthian coins until the time of Vologases I (AD 51–78). Early Parthian rulers used the name of their dynastic founder (Arsaces) as a title. Their coins also have the legend krny (probably short for autokrator, i.e. autocrat or sole ruler). From the conquest of Babylonia onwards, rulers used basileus megas (lit. 'Great King'). Mithridates II (123–91 BC) adopted the Achaemenid 'King of Kings' (rendered in Greek as basileus basileon). After him, this title was used only by Mithridates IV (57–54 BC) and Orodes II (57–37 BC) before becoming a standard part of the Parthian title from the time of Phraates IV (26–2 BC) onwards. The title was used in its Persian form (šāhān šāh) after Greek ceased being used. The first Parthian capital was at Nisa in Parthia. In 217 BC, the capital was moved to Qumis and in 50 BC a multi-capital system was established, with royal residences at Ctesiphon, Ecbatana, and Ray.