An imam (Arabic: إمام, plural: أئمة A'immah; Persian: امام) is an Islamic leadership position. It is most commonly in the context of a worship leader of a mosque and Muslim community by Sunni Muslims only. In this context, Imams may lead Islamic worship services, serve as community leaders, and provide religious guidance. It may also be used in the form of a prefix title with scholars of renown.
Sunni Imams 
The Sunni branch of Islam does not have imams in the same sense as the Shi'a, an important distinction often overlooked by those outside of the Islamic faith. In every day terms, the imam for Sunni Muslims is the one who leads Islamic formal (Fard) prayers, even in locations besides the mosque, whenever prayers are done in a group of two or more with one person leading (imam) and the others following by copying his ritual actions of worship. Friday sermon is most often given by an appointed imam. All mosques have an imam to lead the (congregational) prayers, even though it may sometimes just be a member from the gathered congregation rather than an officially appointed salaried person. Women can not lead prayers except it is an all female maleeha iqbal trained as, and practice, the role of imam among female-only congregations; these are often the wives of imams (see Nusi)). The person that should be chosen according to Hadith is one who has most knowledge of the Qu'ran and is of good character, the age is immaterial.
The term is also used for a recognized religious scholar or authority in Islam, often for the founding scholars of the four Sunni madhhabs, or schools of jurisprudence (fiqh). It may also refer to the Muslim scholars who created the analytical sciences related to Hadith or it may refer to the heads of the Prophet Muhammad's family in their generational times.
The following table shows the considered imams in the context of scholarly authority by Sunni Muslims:
|Madhhab (Schools of Jurisprudence)||Aqidah (Schools of Theology)||Science of Hadith|
|Imam Abu Hanifa||Imam Ahmad ibn Hanbal (Athari)||Imam Bukhari|
|Imam Malik||Imam al-Ashari (Ash'ari)||Imam Abu Dawood|
|Imam Shafi'i||Imam Abu Mansur al-Maturidi (Maturidi)||Imam Muslim|
|Imam Ahmad ibn Hanbal||Wasil ibn Ata (Mu'tazili)||Imam Fakhr al-Razi|
Shi'a imams 
In the Shi'a context, imams have a meaning more central to belief, referring to leaders of the community. Twelver and Ismaili Shi'a believe that these imams are chosen by God to be perfect examples for the faithful and to lead all humanity in all aspects of life. They also believe that all the imams chosen are free from committing any sin, impeccability which is called ismah. These leaders must be followed since they are appointed by God.
Here follows a list of the Twelvers imams:
Sahih Bukhari: Narrated Jabir bin Samura: I heard Muhammad saying, "There will be twelve Muslim rulers." He then said a sentence which I did not hear. My father said, "All of them (those rulers) will be from Quraish."  Sahih Muslim : Narrated Jabir bin Samura: I heard Muhammad saying, "The (Islamic) religion will continue until the Hour (day of resurrection), having twelve Caliphs for you, all of them will be from Quraysh." Sunan Abu Dawood : The Prophet said: "This religion remains standing until there are twelve vicegerents over you, all of them agreeable to the nation, all of them from Quraysh."  Sunan al-Tirmidhi : The Prophet said: "There will be after me twelve Amir (Prince/Ruler), all of them from Quraysh."  Musnad Ahmad ibn Hanbal Masrooq rates that someone asked Abdullah Ibn Masood, "O Abaa Abd al-Rahmaan, did you ask the Messenger of Allah how many caliphs will rule this nation?". Abdullah Ibn Masood replied, "Yes, we did ask the Messenger of Allah and he replied, "Twelve, like the number of chiefs (nuqabaa) of Bani Israel"" 
|Importance||Birthplace (present day country)||Place of death and burial|
|1||Ali ibn Abu Talib
علي بن أبي طالب
Abu al-Hassan or Abu al-Husayn
أبو الحسین or أبو الحسن
(Commander of the Faithful)
|The first imam and the rightful successor of the Prophet of all Shia; however, the Sunnis acknowledge him as the fourth Caliph as well. He holds a high position in almost all Sufi Muslim orders (Turuq); the members of these orders trace their lineage to Muhammad through him.||Mecca, Saudi Arabia||Assassinated by Abd-al-Rahman ibn Muljam, a Kharijite in Kufa, who slashed him with a poisoned sword. Buried at the Imam Ali Mosque in Najaf, Iraq.|
|2||Hassan ibn Ali
الحسن بن علي
|He was the eldest surviving grandson of Muhammad through Muhammad's daughter, Fatimah Zahra. Hasan succeeded his father as the caliph in Kufa, and on the basis of peace treaty with Muawiya I, he relinquished control of Iraq following a reign of seven months.||Medina, Saudi Arabia||Poisoned by his wife in Medina, Saudi Arabia on the orders of the Caliph Muawiya. Buried in Jannat al-Baqi.|
|3||Husayn ibn Ali
الحسین بن علي
|He was a grandson of Muhammad. Husayn opposed the validity of Caliph Yazid I. As a result, he and his family were later killed in the Battle of Karbala by Yazid's forces. After this incident, the commemoration of Husayn ibn Ali has become a central ritual in Shia identity.||Medina, Saudi Arabia||Killed on Day of Ashura (10 Muharram) and beheaded at the Battle of Karbala. Buried at the Imam Husayn Shrine in Karbala, Iraq.|
|4||Ali ibn al-Hussein
علي بن الحسین
|al-Sajjad, Zain al-Abedin
|658-9 – 712
|Author of prayers in Sahifa al-Sajjadiyya, which is known as "The Psalm of the Household of the Prophet."||Medina, Saudi Arabia||According to most Shia scholars, he was poisoned on the order of Caliph al-Walid I in Medina, Saudi Arabia. Buried in Jannat al-Baqi.|
|5||Muhammad ibn Ali
محمد بن علي
(splitting open knowledge)
|Sunni and Shia sources both describe him as one of the early and most eminent legal scholars, teaching many students during his tenure.||Medina, Saudi Arabia||According to some Shia scholars, he was poisoned by Ibrahim ibn Walid ibn 'Abdallah in Medina, Saudi Arabia on the order of Caliph Hisham ibn Abd al-Malik. Buried in Jannat al-Baqi.|
|6||Ja'far ibn Muhammad
جعفر بن محمد
|Established the Ja'fari jurisprudence and developed the Theology of Shia. He instructed many scholars in different fields, including Abu Hanifah and Malik ibn Anas in fiqh, Wasil ibn Ata and Hisham ibn Hakam in Islamic theology, and Jābir ibn Hayyān in science and alchemy.||Medina, Saudi Arabia||According to Shia sources, he was poisoned in Medina, Saudi Arabia on the order of Caliph Al-Mansur. Buried in Jannat al-Baqi.|
|7||Musa ibn Ja'far
موسی بن جعفر
Abu al-Hassan I
أبو الحسن الأول
|Leader of the Shia community during the schism of Ismaili and other branches after the death of the former imam, Jafar al-Sadiq. He established the network of agents who collected khums in the Shia community of the Middle East and the Greater Khorasan.||Medina, Saudi Arabia||Imprisoned and poisoned in Baghdad, Iraq on the order of Caliph Harun al-Rashid. Buried in the Kazimayn shrine in Baghdad.|
|8||Ali ibn Musa
علي بن موسی
|Made crown-prince by Caliph Al-Ma'mun, and famous for his discussions with both Muslim and non-Muslim religious scholars.||Medina, Saudi Arabia||According to Shia sources, he was poisoned in Mashad, Iran on the order of Caliph Al-Ma'mun. Buried in the Imam Reza shrine in Mashad.|
|9||Muhammad ibn Ali
محمد بن علي
|Famous for his generosity and piety in the face of persecution by the Abbasid caliphate.||Medina, Saudi Arabia||Poisoned by his wife, Al-Ma'mun's daughter, in Baghdad, Iraq on the order of Caliph Al-Mu'tasim. Buried in the Kazmain shrine in Baghdad.|
|10||Ali ibn Muhammad
علي بن محمد
Abu al-Hassan III
أبو الحسن الثالث
|Strengthened the network of deputies in the Shia community. He sent them instructions, and received in turn financial contributions of the faithful from the khums and religious vows.||Surayya, a village near Medina, Saudi Arabia||According to Shia sources, he was poisoned in Samarra, Iraq on the order of Caliph Al-Mu'tazz. Buried in the Al Askari Mosque in Samarra.|
|11||Hassan ibn Ali
الحسن بن علي
|For most of his life, the Abbasid Caliph, Al-Mu'tamid, placed restrictions on him after the death of his father. Repression of the Shi'ite population was particularly high at the time due to their large size and growing power.||Medina, Saudi Arabia||According to Shia, he was poisoned on the order of Caliph Al-Mu'tamid in Samarra, Iraq. Buried in Al Askari Mosque in Samarra.|
|12||Muhammad ibn al-Hassan
محمد بن الحسن
|al-Mahdi, Hidden Imam, al-Hujjah
|According to Twelver doctrine, he is the current imam and the promised Mahdi, a messianic figure who will return with Christ. He will reestablish the rightful governance of Islam and replete the earth with justice and peace.||Samarra, Iraq||According to Shia doctrine, he has been living in the Occultation since 872, and will continue as long as God wills it.|
Fatimah, also Fatimah al-Zahraa, daughter of Muhammed (615–632), is also considered infallible but not an imam. Shi'a believe that the last imam will one day return.
Zaidi imams as rulers of Yemen 
In the Zaidi Shiite sect, imams were temporal as well as spiritual leaders who held power in Yemen for more than a thousand years. In 897, a Zaidi ruler, al-Hadi ila'l-Haqq Yahya, founded a line of such imams, a theocratic form of government which survived until the second half of the 20th century. (See details under Zaidiyyah, History of Yemen, Imams of Yemen.)
A manuscript from the Mughal Empire describing the story of an Imam.
Crimean Tatar Imam's teach the Quran.
Imam Shamil, Caucasus
A Bosniak Military Imam in the Austro-Hungarian Army.
See also 
- The imam's Arabic titles are used by the majority of Twelver Shia who use Arabic as a liturgical language, including the Usooli, Akhbari, Shaykhi, and to a lesser extent Alawi. Turkish titles are generally used by Alevi, a fringe Twelver group, who make up around 10% of the world Shia population. The titles for each imam literally translate as "First Ali", "Second Ali", and so forth. Encyclopedia of the Modern Middle East and North Africa. Gale Group. 2004. ISBN 978-0-02-865769-1.
- The abbreviation CE refers to the Common Era solar calendar, while AH refers to the Islamic Hijri lunar calendar.
- Nasr, Seyyed Hossein. "Ali". Encyclopædia Britannica Online. Retrieved 2007-10-12.
- Encyclopedia of the Modern Middle East and North Africa. Gale Group. 2004. ISBN 978-0-02-865769-1.
- Tabatabae (1979), pp.190-192
- Tabatabae (1979), p.192
- "Hasan". Encyclopædia Britannica Online. Retrieved 2007-11-08.
- Tabatabae (1979), pp.194-195
- Madelung, Wilferd. "Hasan ibn Ali". Encyclopaedia Iranica. Retrieved 2008-03-23.
- Tabatabae (1979), p.195
- "al-Husayn". Encyclopædia Britannica Online. Retrieved 2007-11-08.
- Tabatabae (1979), pp.196-199
- Calmard, Jean. "Husayn ibn Ali". Encyclopaedia Iranica. Retrieved 2008-03-23.
- Madelung, Wilferd. "'ALĪ B. AL-ḤOSAYN". Encyclopaedia Iranica. Retrieved 2007-11-08.
- Tabatabae (1979), p.202
- Madelung, Wilferd. "AL-BAQER, ABU JAFAR MOHAMMAD". Encyclopaedia Iranica. Retrieved 2007-11-08.
- Tabatabae (1979), p.203
- Tabatabae (1979), p.203-204
- "Wasil ibn Ata". Encyclopædia Britannica Online. Retrieved 2007-11-08.
- Madelung, Wilferd. "'ALĪ AL-HĀDĪ". Encyclopaedia Iranica. Retrieved 2007-11-09.
- Tabatabae (1979), p.205
- Tabatabae (1979) p. 78
- Sachedina (1988), pp.53-54
- Tabatabae (1979), pp.205-207
- Tabatabae (1979), p. 207
- Madelung, Wilferd. "'ALĪ AL-HĀDĪ". Encyclopaedia Iranica. Retrieved 2007-11-08.
- Tabatabae (1979), pp.208-209
- Halm, H. "'ASKARĪ". Encyclopaedia Iranica. Retrieved 2007-11-08.
- Tabatabae (1979) pp. 209-210
- Tabatabae (1979), pp.209-210
- "Muhammad al-Mahdi al-Hujjah". Encyclopædia Britannica Online. Retrieved 2007-11-08.
- Tabatabae (1979), pp.210-211
- Tabatabae (1979), pp. 211-214
- Encyclopædia Britannica Online. Encyclopædia Britannica, Inc.
- Encyclopædia Iranica. Center for Iranian Studies, Columbia University. ISBN 1-56859-050-4.
- Martin, Richard C. Encyclopaedia of Islam and the Muslim world; vol.1. MacMillan. ISBN 0-02-865604-0.
- Encyclopedia of the Modern Middle East and North Africa. Gale Group. 2004. ISBN 978-0-02-865769-1.
- Corbin, Henry (1993 (original French 1964)). History of Islamic Philosophy, Translated by Liadain Sherrard, Philip Sherrard. London; Kegan Paul International in association with Islamic Publications for The Institute of Ismaili Studies. ISBN 0-7103-0416-1.
- Momen, Moojan (1985). TAn Introduction to Shi`i Islam: The History and Doctrines of Twelve. Yale University Press. ISBN 0-300-03531-4.
- Sachedina, Abdulaziz Abdulhussein (1988). The Just Ruler (al-sultān Al-ʻādil) in Shīʻite Islam: The Comprehensive Authority of the Jurist in Imamite Jurisprudence. Oxford University Press US. ISBN 0-19-511915-0.
- Tabatabae, Sayyid Mohammad Hosayn; Seyyed Hossein Nasr (translator) (1979). Shi'ite Islam. SUNY press. ISBN 0-87395-272-3.
|Look up imam in Wiktionary, the free dictionary.|
|Wikimedia Commons has media related to: Imams|
|Wikisource has the text of the 1905 New International Encyclopedia article Imam.|
- A brief introduction of Twelve Imams
- A Brief History Of The Lives Of The Twelve Imams a chapter of Shi'a Islam (book) by Allameh Tabatabaei
- The Twelve Imams Taken From "A Shi'ite Anthology" By Allameh Tabatabaei
- A Short History of the Lives of The Twelve Imams
- Detailed description of the Shiite belief
- List of Sunni Imams
- International Imam Organization