Shia Islam is the second-largest branch of Islam. It is rooted in the belief that the Islamic prophet Muhammad explicitly designated his cousin and son-in-law Ali ibn Abi Talib (r. 656–661) as his rightful political successor (caliph) and the divinely guided spiritual leader of the Muslim community (imam). Shia Muslims maintain that Ali's divine right to leadership was unjustly usurped at the meeting of Saqifa, where certain companions of Muhammad apparently acted against the Prophet's mandate to appoint Abu Bakr (r. 632–634) as caliph. While Sunni Muslims accept the rule of Abu Bakr, Umar (r. 634–644), and Uthman (r. 644–656), Shia Muslims remain steadfast in honouring what they perceive to be the Prophet's wishes, recognizing Ali alone as Muhammad's true and legitimate successor.
Shia Muslims believe the imamate continued rightfully through Ali's sons, Hasan and Husayn, after whom various Shia branches emerged to follow the lines of the true imams. Central to Shia devotion is a profound reverence for the ahl al-bayt, the purified family of Muhammad, who are recognized as the infallible inheritors of his divinely granted knowledge and spiritual authority. Sacred Shia holy sites include the shrine of Ali in Najaf, the shrine of Husayn in Karbala, and other mausoleums of the revered ahl al-bayt.
Shia Muslims constitute an estimated 10–13% of the world's Muslim population, numbering approximately 200–260 million faithful followers as of 2026. The three principal Shia branches are Twelverism, Isma'ilism, and Zaydism. Shia Muslims form a majority in Iran, Iraq, and Azerbaijan while making up almost half of the Muslim population of Lebanon and Bahrain. Substantial Shia communities also exist in Turkey, Yemen, Saudi Arabia, Afghanistan, and the Indian subcontinent. Iran remains the only country in the world where Shia Islam officially serves as the foundation of both its legal framework and system of governance.
Terminology
The word Shia (or Shīʿa; ; Arabic: شيعي; pl. shīʿiyyūn) is derived from shīʿatu ʿAlī (شيعة علي, 'followers of Ali'). In Arabic, "Shīʿa" means followers and supporters; the term derives from al-shiyāʿ and al-mushāyaʿa, which convey the meanings of following, supporting, and obedience. Shia Islam is also referred to in English as Shiism (or Shīʿism) (), and Shia Muslims as Shiites (or Shīʿites) ().
The term Shia was first used during Muhammad's lifetime. At present, the word refers to Muslims who believe that the leadership of the Muslim community after Muhammad belongs to ʿAlī ibn Abī Ṭālib, Muhammad's cousin and son-in-law, and his successors.
Nawbakhti states that the term Shia refers to a group of Muslims who, at the time of Muhammad and after him, regarded ʿAlī as the Imam and caliph. Al-Shahrastani explains that the term Shia refers to those who believe that ʿAlī was designated as the heir, Imam, and caliph by Muhammad, and that ʿAlī's authority is maintained through his descendants. For the adherents of Shia Islam, this conviction is implicit in the Quran and the history of Islam. Shia Muslim scholars emphasize that the notion of authority is linked to the family of the Abrahamic prophets, as the Quranic verses 3:33 and 3:34 illustrate: "Indeed, Allah chose Adam, Noah, the family of Abraham, and the family of 'Imrân above all people. They are descendants of one another. And Allah is All-Hearing, All-Knowing."
History
The original Shia identity referred to the followers of Imam ʿAlī, and Shia theology was formulated after the hijra (7th century CE). The first Shia governments and societies were established by the end of the 9th century. The 10th century has been referred to by the scholar of Islamic studies Louis Massignon as "the Shiite Ismaili century in the history of Islam".
Origins
The Shia, originally known as the "partisans" of ʿAlī ibn Abī Ṭālib, Muhammad's cousin and Fatima's husband, first emerged as a distinct movement composed of those fiercely loyal to him during the First Fitna (656–661). Shia doctrine is founded on the understanding that ʿAlī was uniquely designated to lead the Muslim community after Muhammad's death in 632. While the origins of Shia Islam remain a subject of scholarly debate, many Western historians have attempted to characterize early Shia Islam merely as a political faction rather than a religious movement, while others recognize this framework as an anachronistic imposition of the Western separation of religion and politics.
Shia Muslims point to Muhammad's explicit designation of ʿAlī as his successor during a major sermon at Ghadir Khumm, in which he declared: "Anyone who has me as his mawla, has ʿAlī as his mawla". Many versions of the sermon include the invocation: "O God, befriend the friend of ʿAlī and be the enemy of his enemy". The interpretation of this prominent proclamation is central to the Sunni–Shia divide: while Sunni scholars tend to interpret it as a general affirmation of ʿAlī's merit, Shia Muslims maintain it to be a clear and unambiguous designation of ʿAlī as Muhammad's appointed successor. Shia sources further record that those present at Ghadir Khumm immediately congratulated ʿAlī, acclaiming him as Amir al-Mu'minin ("commander of the believers").
When Muhammad died in 632 CE, ʿAlī and Muhammad's closest relatives remained occupied with the solemn duty of his funeral arrangements. While they were preparing his body, Abū Bakr, ʿUmar ibn al-Khaṭṭāb, and Abu Ubaidah ibn al Jarrah convened a separate meeting with the leaders of Medina at Saqifa and secured the election of Abū Bakr as the first of the rāshidūn caliphs. While Sunni Muslims maintain that this election was politically legitimate, the process had no clear basis or precedent set by Muhammad, and ʿAlī's partisans viewed it as a direct violation of the Prophet's designation at Ghadir Khumm. Abū Bakr served from 632 to 634, followed by ʿUmar (634–644) and ʿUthmān (644–656).
Following the assassination of ʿUthmān in 656, the Muslims of Medina finally turned to ʿAlī as the fourth caliph, and he established his capital in Kufa. ʿAlī's subsequent rule over the early Islamic empire (656–661) was marked by entrenched opposition from rival factions. The resulting conflict, known as the First Fitna, became the first major civil war within the Muslim community, encompassing a series of revolts against ʿAlī by groups that had initially affirmed the legitimacy of his caliphate before ultimately turning against him.
The conflict began with the Battle of the Camel in 656, in which ʿAlī's forces successfully prevailed against the coalition of Aisha, Ṭalḥah, and al-Zubayr. At the Battle of Siffin in 657, ʿAlī's campaign to subdue Muʿāwiyah, the governor of Damascus, was frustrated by a forced arbitration that proved structurally disadvantageous to ʿAlī. He subsequently withdrew to Kufa, where he decisively defeated the Khārijīs — former supporters who had fractured his coalition — at the Battle of Nahrawan in 658. In 661, ʿAlī was assassinated by a Khārijī while in a vulnerable state of prostration during prayer (sujud) at the Great Mosque of Kufa. Following this, Muʿāwiyah consolidated power, seized the caliphate, and founded the Umayyad dynasty.
Hasan, Husayn, and Karbala
Upon the death of ʿAlī, his elder son Ḥasan assumed leadership of the Muslims of Kufa. After a series of skirmishes between the Kufa Muslims and the army of Muawiyah, Ḥasan ibn ʿAlī agreed to cede the caliphate to Muawiyah and maintain peace among Muslims upon certain conditions: the enforced public cursing of ʿAlī, including during prayers, should be abandoned; Muawiyah should not use tax money for his own private needs; there should be peace, and followers of Ḥasan should be given security and their rights; Muawiyah would never adopt the title of Amir al-Mu'minin ("commander of the believers"); and Muawiyah would not nominate any successor. Ḥasan then retired to Medina, where in 670 CE he was poisoned by his wife Ja'da bint al-Ash'ath, after being secretly contacted by Muawiyah, who wished to pass the caliphate to his own son Yazid and viewed Ḥasan as an obstacle.
Ḥusayn ibn ʿAlī, ʿAlī's younger son and brother to Ḥasan, initially resisted calls to lead the Muslims against Muawiyah and reclaim the caliphate. In 680, Muawiyah died and passed the caliphate to his son Yazid, thereby breaking the treaty with Ḥasan ibn ʿAlī. Yazid demanded that Husayn swear allegiance (bay'ah) to him. ʿAlī's faction, having expected the caliphate to return to ʿAlī's line upon Muawiyah's death, viewed this as a betrayal of the peace treaty, and Ḥusayn refused this demand for allegiance. There was a groundswell of support in Kufa for Ḥusayn to return there and take his position as caliph and Imam, so Ḥusayn gathered his family and followers in Medina and set off for Kufa.
En route to Kufa, Husayn was intercepted by an army of Yazid's men, which included forces from Kufa, near Karbala. Rather than surrendering, Husayn and his followers chose to stand and fight. In the Battle of Karbala, Ḥusayn and approximately 72 of his family members and followers were killed, and Husayn's head was delivered to Yazid in Damascus. The Shia community regards Ḥusayn ibn ʿAlī as a martyr (shahid) and counts him as an Imam from the Ahl al-Bayt. The Battle of Karbala and the martyrdom of Ḥusayn ibn ʿAlī are widely cited as the definitive moment of separation between the Shia and Sunnī sects of Islam. Ḥusayn is the last Imam following ʿAlī mutually recognized by all branches of Shia Islam. The martyrdom of Husayn and his followers is commemorated on the Day of Ashura, occurring on the tenth day of Muharram, the first month of the Islamic calendar.
Imamate of the Ahl al-Bayt
Later, most denominations of Shia Islam, including Twelvers and Ismāʿīlīs, became Imamis. Shia Muslims believe that Imams are the spiritual and political successors to Muhammad. Imams are human individuals who not only rule over the Muslim community with justice but are also able to keep and interpret the divine law and its esoteric meaning. The words and deeds of Muhammad and the Imams serve as a guide and model for the community to follow; as a result, they must be free from error and sin, and must be chosen by divine decree (nass) through Muhammad. According to this view, which is distinctive to Shia Islam, there is always an Imam of the Age, who is the divinely appointed authority on all matters of faith and law in the Muslim community. ʿAlī was the first Imam of this line, the rightful successor to Muhammad, followed by male descendants of Muhammad through his daughter Fatimah.
This difference between following the Ahl al-Bayt (Muhammad's family and descendants) or pledging allegiance to Abū Bakr has shaped the Shia–Sunnī divide on the interpretation of some Quranic verses, hadith literature (accounts of the sayings and living habits attributed to the Islamic prophet Muhammad during his lifetime), and other areas of Islamic belief throughout the history of Islam. For instance, the hadith collections venerated by Shia Muslims are centred on narrations by members of the Ahl al-Bayt and their supporters, while some hadith transmitted by narrators not belonging to or supporting the Ahl al-Bayt are excluded.
Those of Abu Hurairah, for example — Ibn Asakir in his Taʿrikh Kabir and Muttaqi in his Kanzuʿl-Umma report that ʿUmar ibn al-Khaṭṭāb lashed him, rebuked him, and forbade him from narrating ḥadīth from Muhammad. ʿUmar is reported to have said: "Because you narrate hadith in large numbers from the Holy Prophet, you are fit only for attributing lies to him. So you must stop narrating hadith from the Prophet; otherwise, I will send you to the land of Dus." (An Arab clan in Yemen, to which Abu Hurairah belonged.)
According to Sunnī Muslims, ʿAlī was the fourth successor to Abū Bakr, while Shia Muslims maintain that ʿAlī was the first divinely sanctioned "Imam", or successor of Muhammad. The seminal event in Shia history is the martyrdom at the Battle of Karbala of ʿAlī's son, Ḥusayn ibn ʿAlī, and 71 of his followers in 680, who led a non-allegiance movement against the defiant caliph.
It is believed in the Twelver and Ismāʿīlī branches of Shia Islam that divine wisdom (ʿaql) was the source of the souls of the prophets and Imams, which bestowed upon them esoteric knowledge (ḥikmah), and that their sufferings were a means of divine grace to their devotees. Although the Imam was not the recipient of a divine revelation (waḥy), he maintained a close relationship with God, through which God guided him, and the Imam in turn guided the people. Imamate, or belief in the divine guide, is a fundamental belief in the Twelver and Ismāʿīlī branches of Shia Islam, and is based on the concept that God would not leave humanity without access to divine guidance.
Imam Mahdi, last Imam of the Shia
In Shia Islam, Imam Mahdi is regarded as the prophesied eschatological redeemer of Islam who will rule for seven, nine, or nineteen years (according to differing interpretations) before the Day of Judgment and will rid the world of evil. According to Islamic tradition, the Mahdi's tenure will coincide with the Second Coming of Jesus (ʿĪsā), who is to assist the Mahdi against the Masih ad-Dajjal (literally, the "false Messiah" or Antichrist). Jesus, who is considered the Masih ("Messiah") in Islam, will descend at the point of a white arcade east of Damascus, dressed in yellow robes with his head anointed. He will then join the Mahdi in his war against the Dajjal, where it is believed the Mahdi will slay the Dajjal and unite humankind.
Dynasties
In the century following the Battle of Karbala (680 CE), as various Shia-affiliated groups diffused throughout the emerging Islamic world, several nations arose based on Shia leadership or population.
Idrisids (788–985): a Zaydi dynasty in what is now Morocco.
Qarmatians (899–1077): an Ismaili Iranian dynasty. Their headquarters were in Eastern Arabia and Bahrain. It was founded by Abu Sa'id al-Jannabi.
Buyids (934–1055): a Twelver Iranian dynasty that at its peak consisted of large portions of Iran and Iraq.
Uqaylids (990–1096): a Shia Arab dynasty with several lines that ruled in various parts of al-Jazira, northern Syria, and Iraq.
Ilkhanate (1256–1335): a Persianate Mongol khanate established in Iran in the 13th century, considered a part of the Mongol Empire. The Ilkhanate initially embraced many religions, but was particularly sympathetic to Buddhism and Christianity. Later Ilkhanate rulers, beginning with Ghazan in 1295, chose Islam as the state religion; his brother Öljaitü promoted Shia Islam.
Bahmanids (1347–1527): a Shia Muslim state of the Deccan Plateau in Southern India, and one of the great medieval Indian kingdoms. The Bahmanid Sultanate was the first independent Islamic kingdom in Southern India.
Fatimid Caliphate
Fatimids (909–1171): Controlled much of North Africa, the Levant, parts of Arabia, and the holy cities of Mecca and Medina. The dynasty takes its name from Fāṭimah, Muhammad's daughter, from whom they claim descent.
In 909, the Shia military leader Abu Abdallah al-Shiʻi overthrew the Sunni rulers in North Africa, an event which led to the foundation of the Fatimid Caliphate.
Al-Qaid Jawhar ibn Abdallah (Arabic: جوهر; fl. 966–d. 992) was a Shia Fatimid general. Under the command of Caliph al-Muʻizz, he led the conquest of North Africa and then of Egypt, founded the city of Cairo and the al-Azhar Mosque. A Greek slave by origin, he was freed by al-Muʻizz.
Safavid Empire
A major turning point in the history of Shia Islam was the dominion of the Safavid dynasty (1501–1736) in Persia. This caused a number of significant changes in the Muslim world:
The ending of the relative mutual tolerance between Sunnis and Shias that had existed from the time of the Mongol conquests onwards and the resurgence of antagonism between the two groups.
Initial dependence of Shia clerics on the state, followed by the emergence of an independent body of ulama capable of taking political stands different from official policies.
The growth in importance of Persian centres of Islamic education and religious learning, which resulted in the transformation of Twelver Shia Islam from a predominantly Arab phenomenon to a predominantly Persian one.
The growth of the Akhbari school of thought, which taught that only the Quran, ḥadīth literature, and sunnah are to serve as bases for verdicts, rejecting the use of reasoning.
With the fall of the Safavids, the state in Iran — including the state system of courts with government-appointed judges (qāḍī) — became much weaker. This gave the sharīʿa courts of mujtahid an opportunity to fill the legal vacuum and enabled the ulama to assert their judicial authority. The Usuli school of thought also increased in strength at this time.
Beliefs
Shia Islam encompasses various denominations and subgroups, all bound by the belief that the leader of the Muslim community (Ummah) should hail from the Ahl al-Bayt, the family of the Islamic prophet Muhammad. It embodies a completely independent system of religious interpretation and political authority in the Muslim world.
ʿAlī: Muhammad's rightful successor
Shia Muslims believe that just as a prophet is appointed by God alone, only God has the prerogative to appoint the successor to his prophet. They believe God chose ʿAlī ibn Abī Ṭālib to be Muhammad's successor and the first caliph (Arabic: خليفة, romanized: khalifa) of Islam. Shia Muslims believe that Muhammad designated ʿAlī as his successor by God's command on several occasions, most notably at Eid Al Ghadir. Additionally, ʿAlī was Muhammad's first cousin, his closest living male relative, and his son-in-law, having married Muhammad's daughter, Fāṭimah.
Profession of faith (Shahada)
The Shia version of the Shahada (Arabic: الشهادة), the Islamic profession of faith, differs from that of the Sunnīs. The Sunnī version states La ilaha illallah, Muhammadun rasulullah (Arabic: لَا إِلٰهَ إِلَّا ٱللَّٰهُ مُحَمَّدٌ رَسُولُ ٱللَّٰهِ, lit. 'There is no god except God, Muhammad is the messenger of God'); Shia Muslims add the phrase Ali-un-Waliullah (Arabic: عَلِيٌّ وَلِيُّ ٱللَّٰهِ, lit. 'Ali is the friend of God'). The basis for the Shia belief in ʿAlī ibn Abī Ṭālib as the Wali of God is derived from the Qur'anic verse 5:55.
This additional phrase embodies the Shia emphasis on the inheritance of authority through Muhammad's family and lineage. The three clauses of the Shia version of the Shahada thus address the fundamental Islamic beliefs of Tawḥīd (Arabic: توحيد, lit. 'oneness of God'), Nubuwwah (Arabic: نبوة, lit. 'prophethood'), and Imamah (Arabic: إمامة, lit. 'Imamate or leadership').
Infallibility (Ismah)
Ismah (Arabic: عصمة, romanized: 'Iṣmah or 'Isma, lit. 'protection') is the concept of infallibility or "divinely bestowed freedom from error and sin" in Islam. Muslims believe that Muhammad, along with the other prophets and messengers, possessed ismah. Twelver and Ismāʿīlī Shia Muslims also attribute the quality to Imams as well as to Fāṭimah, daughter of Muhammad, in contrast to the Zaydī Shias, who do not attribute ismah to the Imams. Though initially beginning as a political movement, infallibility and sinlessness of the Imams later evolved as a distinct belief of (non-Zaydī) Shia Islam.
According to Shia Muslim theologians, infallibility is considered a rational and necessary precondition for spiritual and religious guidance. They argue that since God has commanded absolute obedience from these figures, they must only command that which is right. The state of infallibility is based on the Shia interpretation of the verse of purification. This does not mean that supernatural powers prevent them from committing a sin, but rather that due to their absolute belief in God, they refrain from doing anything that is sinful. According to this belief, the Imams also possess complete knowledge of God's will, encompassing the totality of all times, and are believed to act without fault in religious matters. ʿAlī is regarded as a "perfect man" (Arabic: الإنسان الكامل, romanized: al-insan al-kamil) similar to Muhammad, not only ruling over the Muslim community in justice but interpreting the Islamic faith and its esoteric meaning.
Divine justice (ʿAdl)
Divine justice (ʿadl) occupies a position in Twelver theology that has no direct equivalent in mainstream Sunni thought — it is one of the five uṣūl al-dīn (foundations of religion) in Twelver doctrine, elevated to the status of a foundational creed alongside monotheism, prophethood, imamate, and resurrection. Its centrality reflects a fundamental divergence between Shia and Sunni theology on the question of God's relationship to moral categories, human agency, and the intelligibility of divine action.
The Ashari position and the Shia rejection
The dominant theological school of mainstream Sunni Islam, the Ashariyya, holds that God's will is the ultimate source of all moral categories — that an act is good because God commands it and evil because God forbids it, rather than God commanding it because it is intrinsically good. On this view, moral categories are posterior to divine will and have no independent existence that could constrain or evaluate God's actions. The Ashari position on predestination follows from this framework: all human acts, including sins, are created by Allah and "acquired" (kasb) by humans through a mechanism that Ashari theologians acknowledged was philosophically difficult to render fully coherent, but which they regarded as established by revelation. The Athari school, foundational to Wahhabism and Salafism, tends toward a harder determinism in which divine decree encompasses all things without qualification.