Shia Islam

Overview

Shia Islam is the smaller of Islam's two great branches; the larger is Sunni Islam. Its name comes from shīʿat ʿAlī, "the party of ʿAlī". Shia share with other Muslims faith in one God, in Muhammad and in the Qur'an. What sets them apart is the conviction that leadership after Muhammad belonged by right to his cousin and son-in-law ʿAlī, then to imams descended from ʿAlī and the Prophet's daughter Fāṭima. The killing of ʿAlī's son Ḥusayn at Karbala in 680 is mourned every year. Most Shia are Twelvers, who hold that the twelfth imam lives on in hiding; Ismāʿīlīs and Zaydīs are smaller branches. Shia are roughly a tenth to an eighth of all Muslims, a majority in Iran, Iraq, Azerbaijan and Bahrain, with large communities in Pakistan, India and Lebanon.^{[1, 3–4, 10–16]}

History

ʿAlī and the question of succession 632–661

When Muhammad died in 632, leading Muslims in Medina chose Abū Bakr as caliph. Some held that the rightful heir was ʿAlī, the Prophet's cousin and son-in-law. Shia sources say Muhammad had named him at Ghadīr Khumm, on the road home from his last pilgrimage: "Whoever has me as his mawlā has ʿAlī as his mawlā." Sunnis accept that the Prophet spoke there but not that he made an appointment. ʿAlī became the fourth caliph in 656 and ruled from Kufa through civil war until a Khārijite attacked him in 661.^{[1, 17–20]}

Karbala and the line of imams 680–765

When the Umayyad caliph Muʿāwiya died in 680, ʿAlī's younger son Ḥusayn refused allegiance to his heir Yazīd and set out for Kufa, whose supporters had invited him. On 10 Muḥarram (October 680) an Umayyad army killed him and some seventy companions at Karbala. In Shia belief, leadership passed to imams among Ḥusayn's descendants, endowed with God-given knowledge. Successions divided the community: in 740 Ḥusayn's grandson Zayd died leading a revolt, inspiring the Zaydīs, and when the sixth imam, Jaʿfar al-Ṣādiq, died in 765, some followed the line of his son Ismāʿīl, others his son Mūsā.^[21–25]

Occultation and the classical age 874–1171

When the eleventh imam in Mūsā's line, Ḥasan al-ʿAskarī, died in 874, his followers split again. The view that prevailed held that his young son was alive but hidden. Twelvers count a "lesser occultation", when four agents relayed the hidden imam's word, ending in 941, and a "greater occultation" that continues. Scholars took up the work of guidance: al-Kulaynī compiled al-Kāfī, and under the Shia Būyids, who controlled Baghdad from 945 to 1055, Twelver learning flourished. Meanwhile the Ismāʿīlī Fāṭimids founded a caliphate in North Africa in 909, built Cairo in 969 and ruled Egypt until 1171.^[26–29]

Safavid Iran 1501–1800s

Iran was still mostly Sunni in 1501, when Ismāʿīl, head of the Safavid Sufi order, took Tabriz, was crowned shah and made Twelver Shiism the state religion. The change began by force: resisters were threatened with death, leading Sunnis were killed, some towns were massacred, and many Sunni scholars emigrated. Arab Shia scholars from Jabal ʿĀmil in today's Lebanon, Iraq and the Gulf came to teach, and Muḥarram mourning grew more elaborate. By 1722 most Iranians were Shia. Later the Uṣūlī school prevailed, giving trained jurists, the mujtahids, wide authority while the imam is hidden.^[30–34]

The modern era 1900s–today

In 1978–79 a broad uprising in Iran, voiced through Shia ritual and symbols, toppled the shah. A new constitution built on Khomeini's doctrine of velāyat-e faqīh, "guardianship of the jurist", put a senior cleric at the head of the state; Khamenei held that post from 1989 to 2026, when he was killed; the Assembly of Experts named his son Mojtaba as successor. Many Shia scholars dispute the idea; Najaf jurists such as ʿAlī al-Sīstānī take a quieter line. In Iraq, the Baʿth regime persecuted Shia clergy and crushed a 1991 uprising; after 2003 Shia parties gained power and pilgrimage returned. Among Ismāʿīlīs, Aga Khan IV, imam since 1957, died in 2025 and was succeeded by his son Rahim as the 50th imam, Aga Khan V.^[35–39]

Key moments

1. 632 CEMuhammad's death and the first caliph · Medina
2. 680 CEKarbala · Karbala, Iraq
3. 1979 CEThe Iranian Revolution · Tehran, Iran

Beliefs

Imamate · إمامة

leadership of the community by the imam

Shia teach that God did not leave the community without a guide after Muhammad. The guide is the imam, a descendant of ʿAlī and Fāṭima chosen by God and named by his predecessor. Twelvers hold the imams free from sin and error and heirs to special knowledge, including the Qur'an's true sense; they count twelve, from ʿAlī to Muḥammad al-Mahdī.^{[5, 15, 23]}

Ahl al-Bayt · أهل البيت

people of the house

Love for the Prophet's household is at the heart of Shia devotion. The Qur'an (33:33) speaks of the "people of the house", which Shia understand as the Prophet's family through Fāṭima and ʿAlī. They also cite a report, found in some Sunni collections too, that Muhammad left behind "two weighty things", the Qur'an and his family.^[40]

Occultation and the Mahdī · غيبة

absence, concealment

Twelvers believe the twelfth imam has lived hidden since the 9th century and will return at the end of time as the Mahdī, "the rightly guided one", also called the Qāʾim, "the one who rises", to fill the world with justice.^{[26–27, 41]}

Martyrdom and Karbala · شهادة

witness, martyrdom

Ḥusayn's death at Karbala stands, for Shia, as the model of standing for justice against tyranny, even at the cost of one's life. Retelling his suffering is itself counted a meritorious act. Sunnis also honour Ḥusayn as the Prophet's grandson, and many regard his death as a model of self-sacrifice.^{[14, 42]}

Ijtihād and taqlīd · اجتهاد / تقليد

legal reasoning / following

Twelvers divide believers into mujtahids, scholars trained to derive rulings from the Qur'an and the reports of the Prophet and imams, and everyone else, who follow a living mujtahid of their choice. The most senior are called marjaʿ al-taqlīd, "source of emulation", an institution that took shape in the 19th century.^{[7, 43]}

Ismāʿīlī imamate · إسماعيلية

Ismāʿīlīs trace the imamate through Jaʿfar's son Ismāʿīl. The largest group, the Nizārīs, follow a living imam, the Aga Khan, and emphasise the inner meaning of faith alongside its outward forms. The Mustaʿlī-Ṭayyibī Ismāʿīlīs, chiefly the Bohras of South Asia, hold that their imam is hidden and are led by a deputy called the dāʿī.^{[8, 44]}

Zaydī imamate · زيدية

Zaydīs accept as imam any learned and upright descendant of Ḥasan or Ḥusayn who openly claims leadership, rather than a fixed hereditary line. In law and doctrine Zaydīs are often regarded as the Shia branch closest to Sunni Islam. They live mainly in northern Yemen, where Zaydī imams held power from 897 until the last was overthrown in 1962.^[45]

Alawites and Alevis · علويون / Aleviler

Two communities honour ʿAlī but stand apart from the main branches. The Alawites, chiefly in Syria, keep an esoteric doctrine largely private; whether they are Shia is debated, though the Lebanese Shia leader Mūsā al-Ṣadr recognised them in 1973. The Alevis of Turkey revere ʿAlī and the twelve imams but worship in their own cem gatherings; their roots lie in the Kizilbash movement that backed the Safavids, though many Alevis do not describe themselves as Shia.^[46–47]

Practice

Mourning in Muḥarram · عزاء

In the first ten days of Muḥarram, Shia gather in assemblies to hear sermons and elegies on Karbala, often ending in rhythmic chest-beating. Processions in Iran and South Asia carry models of Ḥusayn's tomb, and Iran's taʿziya passion play took shape by the 18th century. Some men draw blood in self-flagellation, a debated practice that Ayatollah Khamenei forbade in 1994.^[48–50]

Pilgrimage to the shrines · زيارة

Besides the hajj to Mecca, Shia make ziyāra, devotional visits to the tombs of the imams and their families. Visits to Karbala were established practice by the 9th century. For Arbaʿīn many walk some 80 km from Najaf to Karbala, fed by volunteers at roadside stations; numbers grew from about 2 million in 2003 to around 20 million.^[51–52]

Following a marjaʿ

A Twelver who is not a qualified scholar follows the rulings of a chosen marjaʿ. Believers also pay religious dues, notably khums, "a fifth" of certain income, through their marjaʿ. These payments have long given the Shia clergy financial independence from governments.^{[7, 53–54]}

Jaʿfarī law

Twelver law is called Jaʿfarī after the sixth imam. In 1959 the rector of al-Azhar in Cairo, Maḥmūd Shaltūt, declared it a legitimate school alongside the four Sunni schools. Twelver law permits fixed-term marriage (mutʿa), holding that the caliph ʿUmar, not the Prophet, banned it, while most Sunnis regard it as abolished.^[55–56]

Holy days

Ashura · عاشوراء

10 Muḥarram (moves through the solar year)

The anniversary of Ḥusayn's death at Karbala and the climax of ten days of mourning, with assemblies, processions and passion plays. Sunnis also mark the day, as an optional fast.^{[48, 57]}

Arbaʿīn · الأربعين

20 Ṣafar, forty days after Ashura (moves through the year)

Ends the forty days of mourning for Ḥusayn. By tradition the Companion Jābir ibn ʿAbd Allāh first visited his grave on this day; today it draws one of the world's largest pilgrimages to Karbala.^{[52, 58]}

Eid al-Ghadīr · عيد الغدير

18 Dhū al-Ḥijja (moves through the year)

A festival marking the day Shia believe Muhammad appointed ʿAlī as his successor at Ghadīr Khumm in 632, as he travelled home from his last pilgrimage.^{[18, 59]}

People

ʿAlī ibn Abī Ṭālib · علي بن أبي طالب

other · d. 661

Cousin and son-in-law of Muhammad and the fourth caliph, ʿAlī is for Shia the first imam and the Prophet's rightful heir. Sermons and sayings attributed to him are gathered in the Nahj al-Balāgha, and his shrine is at Najaf.^[60–62]

Fāṭima · فاطمة الزهراء

other · c. 605–632/633

Muhammad's daughter, Fāṭima married ʿAlī and was the mother of Ḥasan and Ḥusayn, so every imam descends from her. After her father's death she clashed with Abū Bakr over her inheritance and died months later. Shia honour her deeply.^[63]

Ḥusayn ibn ʿAlī · الحسين بن علي

other · c. 626–680

Younger son of ʿAlī and Fāṭima and the third imam, Ḥusayn refused allegiance to Yazīd and was killed at Karbala with his companions. His head was carried to Yazīd in Damascus. His tomb at Karbala draws one of the largest annual pilgrimages in the world.^{[21, 52, 64]}

Jaʿfar al-Ṣādiq · جعفر الصادق

scholar · c. 700–765

The sixth imam, and the last recognised by all Shia branches, taught in Medina. Twelver law bears his name. Sunnis also valued him as a jurist and transmitter of hadith, and the founders of two Sunni schools, Abū Ḥanīfa and Mālik, are reported to have studied with him.^{[55, 65]}

Muḥammad al-Mahdī · محمد المهدي

other

The twelfth imam, son of Ḥasan al-ʿAskarī, is believed by Twelvers to have gone into occultation as a small child after his father's death in 874. They await his return as the Mahdī, who will fill the world with justice.^{[41, 66]}

Scripture

The Qur'an · القرآن

7th century

Shia, like all Muslims, hold the Qur'an to be God's word revealed to Muhammad. Shia exegesis holds that its authoritative interpretation passed to ʿAlī and the imams, and reads verses such as 33:33 in that light. Al-Ṭūsī's al-Tibyān is among the classic Shia commentaries.^{[5, 13, 40]}

Nahj al-Balāgha · نهج البلاغة

c. 1000 CE

"The Path of Eloquence" gathers sermons, letters and sayings attributed to ʿAlī, compiled by the Shia scholar al-Sharīf al-Raḍī. Some Western scholars have questioned how much goes back to ʿAlī, but it is read across the Muslim world, by Sunnis as well as Shia, for its thought and style.^[61]

Al-Kāfī and the Four Books · الكافي

10th–11th century

Al-Kāfī ("The Sufficient") of al-Kulaynī, who died in 941, holds over 16,000 reports from the Prophet and the imams on belief, ritual and law. It is the oldest of the Four Books that Twelvers treat as their core hadith collections.^[6]

Places

Shrine of Imam ʿAlī, Najaf

IRQ

ʿAlī's gold-plated shrine stands at the heart of Najaf, beside the vast Wadi al-Salam cemetery. The city has been a centre of Shia learning since the scholar al-Ṭūsī settled there in the 11th century, and Khomeini lived there in exile.^[62]

Shrine of Imam Ḥusayn, Karbala

IRQ

Ḥusayn's tomb, and nearby that of his half-brother ʿAbbās, mark the battlefield of 680. Wahhabi raiders sacked the shrine in 1801 and it was rebuilt. It is the goal of the Arbaʿīn pilgrimage.^[67]

Shrine of Imam Riḍā, Mashhad

IRN

The tomb of the eighth imam, ʿAlī al-Riḍā, who died nearby in 818, is the only imam's grave in Iran; the city of Mashhad grew up around it. A vast endowment runs the shrine.^[68–69]

Shrine of Fāṭima al-Maʿṣūma, Qom

IRN

The tomb of the eighth imam's sister, who died in Qom in 816 or 817, under a golden dome. Qom is also home to Iran's largest seminary and was Khomeini's base.^[70–71]

ʿAskarī Shrine, Samarra

IRQ

The tombs of the tenth and eleventh imams, ʿAlī al-Hādī and Ḥasan al-ʿAskarī, form one of the holiest Twelver shrines. Twelvers also revere Samarra as the place where the twelfth imam went into occultation.^[72]

Art & objects

Public-domain objects from museum collections. Select one to see it at the museum.

Khamsa StandardIran, Qajar dynasty (1789-1925), c. early 19th centuryCeremonial Standard ('Alam)India, 17th/18th centuryPlaque with Qur'anic InscriptionIran, Safavid dynasty (1501–1736), 16th centuryShah Tahmasp I (1514–1576) Seated in a LandscapeIran, Qazvin, Safavid period (1501-1722), c. 1575Prayer Niche (Mihrab)Iran, Isfahan, in the style of the Safavid period (1501–1722), c. 1500s or mid-1900sFragment of a Standard ('Alam)17th centuryFragment of a Processional Standard ('Alam)late 16th centuryProcessional Standard ('Alam)late 17th–early 18th century

Numbers

Shia Muslims worldwide

c. 200–260 million (derived estimate)^[11]

Derived, not a published count: Pew (2009) put Shia at 10–13% of Muslims, 154–200 million then; applying that same share to Pew's c. 2.0 billion Muslims in 2020 gives this range.

Share of the world's Shia living in Iran

about 37–40% (2009)^[73]

National censuses

Source: Stats NZ, 2018 Census, licensed by Stats NZ for re-use under the Creative Commons Attribution 4.0 International licence.

How we know

What the sources say about succession

Historians agree that the earliest sources record no formal deathbed appointment by Muhammad. Shia point instead to earlier reports, above all Ghadīr Khumm and the saying about the Qur'an and the Prophet's family, which also appear in Sunni collections. Sunni scholars accept that these events happened but read them as praise of ʿAlī rather than appointment. Much therefore turns on how one word, mawlā, is understood.^{[19, 40]}

How Twelver Shiism took shape

Scholars see Twelver doctrine forming over decades. After the eleventh imam died in 874, a time Shia writers themselves called the "perplexity", believers split into many groups, and only a minority at first held that a hidden son lived. The earliest surviving text listing all twelve imams dates from the early 10th century. Some historians doubt that the doctrine of an infallible imam was fully formed before then.^[74]

Common misconceptions

Glossary

Ahl al-Bayt · أهل البيت

"People of the house": the Prophet's family, especially Fāṭima, ʿAlī, Ḥasan, Ḥusayn and the imams.^[40]

Mahdī · مهدي

"The rightly guided one", a deliverer expected at the end of time; for Twelvers, the hidden twelfth imam.^[78]

Marjaʿ al-taqlīd · مرجع التقليد

"Source of emulation": a senior jurist whose rulings his followers adopt. He is expected to publish a handbook applying the law to daily life.^[53]

Mujtahid · مجتهد

A scholar qualified to practise ijtihād, independent legal reasoning. "Ayatollah" became a title for senior mujtahids in the 20th century.^[79]

Khums · خمس

"A fifth": a religious due that Twelvers pay, largely through their marjaʿ.^[54]

Ḥawza · حوزة

A Shia seminary, above all those of Najaf and Qom.^[80]

Majlis · مجلس

A gathering, especially a mourning assembly in Muḥarram with a sermon and elegies recounting Karbala.^[48]

Taʿziya · تعزیه

A passion play re-enacting Karbala, developed in Iran. In South Asia, tazia also names the model tombs carried in Muḥarram processions.^[48–49]

ʿAtabāt · العتبات

"The thresholds": the four Iraqi shrine cities of Najaf, Karbala, Kāẓimayn and Samarra.^[81]

Velāyat-e faqīh · ولایت فقیه

"Guardianship of the jurist": Khomeini's doctrine that a qualified jurist should rule in the imam's absence, the basis of Iran's 1979 constitution.^{[35, 71]}