The Caliph (Arabic: خليفة; /khalīfah/) is the head of state in a Caliphate, and the title for the leader of the Islamic Ummah, an Islamic community ruled by the Shari'ah. It is a transcribed version of the Arabic word خليفة Khalīfah (help·info) which means "successor" or "representative". The early leaders of the Muslim nation following Muhammad's (570–632) death were called "Khalifat Rasul Allah", the political successors to the messenger of God (referring to Muhammad). Some academics prefer to transliterate the term as Khalīfah.
Caliphs were often also referred to as Amīr al-Mu'minīn (أمير المؤمنين) "Commander of the Faithful", Imam al-Ummah, Imam al-Mu'minīn (إمام المؤمنين), or more colloquially, leader of the Muslims. After the first four caliphs (Abu Bakr, Umar ibn al-Khattab, Uthman ibn Affan, and Ali ibn Abi Talib), the title was claimed by the Umayyads, the Abbasids, the Fatimids, and the Ottomans, and at times, by competing dynasties in Spain, Northern Africa, and Egypt. Most historical Muslim governors were called sultans or amirs, and gave allegiance to a caliph, but at times had very little real authority. The title has been defunct since the Republic of Turkey abolished the Ottoman Caliphate in 1924, although some individuals and groups have called for its restoration. (Sharif/King Hussein of the Hejaz claimed the title briefly in 1924, and the Imams of Yemen had been using the title for centuries and continued to use the title till 1962.)
Fred Donner, in his book The Early Islamic Conquests (1981), argues that the standard Arabian practice at the time was for the prominent men of a kinship group, or tribe, to gather after a leader's death and elect a leader from amongst themselves. There was no specified procedure for this shura, or consultation. Candidates were usually from the same lineage as the deceased leader, but they were not necessarily. Capable men who would lead well were preferred over an ineffectual heir.
However, this was before the start of Islam, and Sunni Muslims believe and confirm that Muhammad's Father-in-law Abu Bakr was chosen by the community and that this was the proper procedure. They further argue that a caliph may be ideally chosen by election or community consensus.
Shi'a Muslims disagree. They believe that since Muhammad had given many indications that ˤAlī ibn Abī Talib, his cousin and son-in-law, is his chosen successor, regardless of decision via shura. ˤAlī and his descendants are believed to have been the only proper Muslim leaders, or imams in the Shia's point of view. This matter is covered in much greater detail in the article Succession to Muhammad and in the article on Shi'a Islam.
A third branch of Islam, the Ibadi Kharijites, believes that the caliphate rightly belongs to the greatest spiritual leader among Muslims, regardless of his lineage. They are currently an extremely small sect, found mainly in Oman.
Caliph is translated from the Arabic Khalifa (خليفة ẖalīfä) meaning "successor", "substitute", or "lieutenant". It is used in the Qur'an to establish Adam's role as representative of Allah on earth. Kalifa is also used to describe the belief that man's role, in his real nature, is as kalifa or viceroy to Allah. The word is also most commonly used for the Islamic leader of the Ummah; starting with the Prophet Muhammad and his line of successors.
The more general meaning of Khalifa refers to the successors of the Prophet Muhammad. The first four Caliphs: Abu Bakr as-Siddiq, Umar ibn al-Khattab, Uthman ibn Affan, and Ali ibn Abi Talib are commonly known by Sunnis, mainly, as the Khulfa-e-Rashideen ("rightly guided successors"), or "patriarchal" Caliphs. This is because each was a close companion of the Prophet during his prophethood. They are therefore seen as having a direct succession to the Prophet.
Sunni and Shi'a Muslims differ on the legitimacy of the reigns of the Khulfa-e-Rashideen, the first four Caliphs. The Sunnis follow the Caliphates of all four, while the Shi'ites recognize only the Caliphate of Ali and the short Caliphate of his son Hasan. This schism occurred following the death of the Prophet Muhammad.
According to Sunni beliefs, Muhammad gave no specific directions as to the choosing of his successor when he died. At this time there were two customary means of selecting a leader: having a hereditary leader for general purposes, and choosing someone with good qualities in times of crisis or opportunities for action. Both methods were advocated by different groups among the early Muslims, which led to the early division between the Sunnis and Shi'ites.
While Sunni and Shia Islam differ sharply on the conduct of a caliph and the right relations between a leader and a community, they do not differ on the underlying theory of stewardship. Both abhor waste of natural resources in particular to show off or demonstrate power. Many consider this conservation urge a necessity of any desert culture, where oases are precious and natural capital must be preserved, in particular clean water sources.
In the initial stages the latter way of choosing leadership prevailed among the leading companions of the Prophet. Abu Bakr was elected as the first caliph or successor to Muhammad, with the other companions of Muhammad giving an oath of allegiance to him. Those opposing this method thought that Ali, Muhammad's nearest relative, should have succeeded him. However the appointment of the next two caliphs varied from the election of Abu Bakr. On his deathbed, Abu Bakr appointed Umar as his successor without an election by the community of Believers. The oath, approving the appointment of Umar, was taken only by the Companions present in Medina at the time. This led to certain groups disputing the authority of Umar. Umar also altered the way his successor would be found. Before he was assassinated, Umar decided that his successor would come from a group of six. This group included Ali and Uthman another companion of the Prophet. These six would have to establish from among themselves Umar's successor. Ultimately Uthman was chosen as Umar successor, becoming the third Caliph. After the assassination of Uthman, Ali was elected as the fourth Caliph.
Ali's reign as Caliph was plagued by great turmoil and internal strife. Ali was faced with multiple rebellions and insurrections. The primary one coming from Mu'awiyah a relative of Uthman and Governor of Damascus. Mu'awiyah attacked Ali at the Battle of Siffin. The battle lasted several months resulting in a stalemate. In order to avoid further bloodshed, Ali agreed to negotiate with Mu'waiyah. This caused a faction of some 4,000 strict traditionalists, known as Kharijites ("Seceders"), to abandon the fight. After defeating the Kharijites at the Battle of Nahrawan, Ali would later be assassinated by the Kharijite Ibn Muljam. Ali's son Hasan was elected as the fifth Caliph only to concede his title to Mu'awiyah a few months later. Mu'awiyah became the sixth Caliph, establishing the Ummayyad Dynasty.
Under the Umayyads, the Muslim empire grew rapidly. To the West, Muslim rule expanded across North Africa and into Spain. To the East, it expanded through Iran and ultimately to India. This made it one of the largest empires in the history of West Eurasia, extending its entire breadth.
However, the Umayyad dynasty was not universally supported within Islam itself. Some Muslims supported prominent early Muslims like az-Zubayr; others felt that only members of Muhammad's clan, the Banū Hashim, or his own lineage, the descendants of ˤAlī, should rule. There were numerous rebellions against the Umayyads, as well as splits within the Umayyad ranks (notably, the rivalry between Yaman and Qays). Eventually, supporters of the Banu Hisham and Alid claims united to bring down the Umayyads in 750. However, the Shiˤat ˤAlī, "the Party of ˤAlī", were again disappointed when the Abbasid dynasty took power, as the Abbasids were descended from Muhammad's uncle, Abbas ibn Abd al-Muttalib and not from ˤAlī. Following this disappointment, the Shiˤat ˤAlī finally split from the majority Sunni Muslims and formed what are today the several Shiˤa denominations.
The Abbasids would provide an unbroken line of caliphs for over three centuries, consolidating Islamic rule and cultivating great intellectual and cultural developments in the Middle East. But by 940 the power of the caliphate under the Abbasids was waning as non-Arabs, particularly the Turkish (and later the Mamluks in Egypt in the latter half of the 13th century), gained influence, and sultans and emirs became increasingly independent. However, the caliphate endured as both a symbolic position and a unifying entity for the Islamic world.
During the period of the Abassid dynasty, Abassid claims to the caliphate did not go unchallenged. The Shiˤa Said ibn Husayn of the Fatimid dynasty, which claimed descendancy of Muhammad through his daughter, claimed the title of Caliph in 909, creating a separate line of caliphs in North Africa. Initially covering Morocco, Algeria, Tunisia and Libya, the Fatimid caliphs extended their rule for the next 150 years, taking Egypt and Palestine, before the Abbassid dynasty was able to turn the tide, limiting Fatimid rule to Egypt. The Fatimid dynasty finally ended in 1171. The Umayyad dynasty, which had survived and come to rule over the Muslim provinces of Spain, reclaimed the title of Caliph in 929, lasting until it was overthrown in 1031.
The Fatimid Caliphate or al-Fātimiyyūn (Arabic الفاطميون) was an Arab Shi'a dynasty that ruled over varying areas of the Maghreb, Egypt, Sicily, Malta and the Levant from 5 January 909 to 1171. The caliphate was ruled by the Fatimids, who established the Egyptian city of Cairo as their capital. The term Fatimite is sometimes used to refer to the citizens of this caliphate. The ruling elite of the state belonged to the Ismaili branch of Shi'ism. The leaders of the dynasty were also Shia Ismaili Imams, hence, they had a religious significance to Ismaili Muslims. They are also part of the chain of holders of the office of Caliph, as recognized by most Muslims. Therefore, this constitutes a rare period in history in which some form of the Shia Imamate and the Caliphate were united to any degree, excepting the Caliphate of Ali himself.
With exceptions, the Fatimids were reputed to exercise a degree of religious tolerance towards non-Ismaili sects of Islam as well as towards Jews, Maltese Christians and Coptic Christians.
1258 saw the conquest of Baghdad and the execution of Abassid caliph al-Musta'sim by Mongol forces under Hulagu Khan. A surviving member of the Abbasid House was installed as Caliph at Cairo under the patronage of the Mamluk Sultanate three years later. However, the authority of this line of Caliphs was confined to ceremonial and religious matters, and later Muslim historians referred to it as a "shadow" caliphate.
As the Ottoman Empire grew in size and strength, Ottoman rulers beginning with Mehmed II began to claim caliphal authority. Their claim was strengthened when the Ottoman Empire defeated the Mamluk Sultanate in 1517 and took control of most Arab lands. The last Abbasid Caliph at Cairo, al-Mutawakkil III, was taken into custody and was transported to Istanbul, where he surrendered the Caliphate to Selim I.
Ottoman rulers were known primarily by the title of Sultan.
According to Barthold, the first time the title of caliph was used as a political instead of symbolic religious title by the Ottomans was the peace treaty with Russia in 1774. The outcome of this war was disastrous for the Ottomans. Large territories, including those with large Muslim populations such as Crimea, were lost to the Christian Russian Empire. However, the Ottomans under Abdulhamid I claimed a diplomatic victory, the recognition of themselves as protectors of Muslims in Russia as part of the peace treaty. This was the first time the Ottoman caliph was acknowledged as having political significance outside of Ottoman borders by a European power. As a consequence of this diplomatic victory, as the Ottoman borders were shrinking, the powers of the Ottoman caliph increased.
Around 1880 Sultan Abdulhamid II reasserted the title as a way of countering creeping European colonialism in Muslim lands. His claim was most fervently accepted by the Muslims of British India. By the eve of the First World War, the Ottoman state, despite its weakness vis-à-vis Europe, represented the largest and most powerful independent Islamic political entity. But the sultan also enjoyed some authority beyond the borders of his shrinking empire as caliph of Muslims in Egypt, India and Central Asia.
Occasional demonstrations have been held calling for the reestablishment of the Caliphate.
In Morocco, the Sherifian Monarch awarded the title Khalifa or Chaliphe, here meaning 'Viceroy', to royal princes (styled Moulay), including future Sultans, who represented the crown in a part of the sultanate:
Khalifa can have a definition, be a first name, or family or tribe name. Like many titles, Khalifa also occurs in many names.
The question of who should succeed Muhammad was not the only issue that faced the early Muslims; they also had to clarify the extent of the leader's powers. Muhammad, during his lifetime, was not only the Muslim political leader, but the Islamic prophet. All law and spiritual practice proceeded from Muhammad. Nobody claimed that his successor would be a prophet; succession referred to political authority. The uncertainty centered on the extent of that authority. Muhammad's revelations, claiming to be directly from God, were soon codified and written down as the Qur'an, which was accepted as a supreme authority, limiting what a caliph could legitimately command.
However, there is some evidence that some early caliphs did believe that they had authority to rule in matters not specified in the Qur'an. They believed themselves to be temporal and spiritual leaders even in issues not commanded in the Quran, and insisted that implicit obedience to the caliph in all things not contradicting the Quran, was the hallmark of the good Muslim. The modern scholars Patricia Crone and Martin Hinds, in their book God's Caliph, outline the evidence for an early, expansive view of the caliph's importance and authority. They argue that this view of the caliph was eventually nullified (in Sunni Islam, at least) by the rising power of the ulema, or Islamic lawyers, judges, scholars, and religious specialists. The ulema insisted on their right to determine what was legal and orthodox. The proper Muslim leader, in the ulema's opinion, was the leader who enforced the rulings of the ulema, rather than making rulings of his own, unless he himself was qualified in Islamic law. Conflict between caliph and ulema, akin to a modern judiciary, was a recurring theme in early Islamic history, and ended in the victory of the ulema. The caliph was henceforth limited to temporal rule only. He would be considered a righteous caliph if he were guided by the ulema. Crone and Hinds argue that Shi'a Muslims, with their expansive view of the powers of the imamate, have preserved some of the beliefs of the early Ummayad dynasty which ironically, they despise. Crone and Hinds' thesis is not accepted by some scholars.
Most Sunni Muslims now believe that the caliph has always been a merely temporal ruler, and that the ulema has always been responsible for adjudicating orthodoxy and Islamic law (shari'a). The first four caliphs are called the Rashidun, the Rightly Guided Caliphs, because they are believed to have followed the Qur'an and the way or sunnah of Muhammad in all things. This formulation itself presumes the Sunni ulema's view historically.
It has been recorded that Muhammad has said:
"The children of Israel have been governed by Prophets; whenever a Prophet died another Prophet succeeded him; but there will be no prophet after me. There will be caliphs and they will number many (in one time); they asked: What then do you order us? He said: Fulfil bayah to them, only the first of them, the first of them, and give them their dues; for verily Allah will ask them about what he entrusted them with"
"When the oath of allegiance has been taken for two Caliphs, kill the latter of them". 
Abu-Bakr Muhammad's primary disciple is reported to have said:
"It is forbidden for Muslims to have two Amirs for this would cause differences in their affairs and concepts, their unity would be divided and disputes would break out amongst them. The Sunnah would then be abandoned, the bida'a (innovations) would spread and Fitna would grow, and that is in no one's interests".
Ibn Khaldun the famous 14th century Muslim scholar, economist and historian said: "It is not possible to appoint two men to the position (of caliph) at the same time. Religious scholars generally are of this opinion, on the basis of certain hadith(recorded statements) of Muhammad. Those hadith are found in the book entitled, "On Leadership (imarah)," in Sahih Muslim. They expressly indicate that this is so."
“Our (scholarly) associates agree on precluding the investing of two different individuals with the imamate at either end of the world. But, they add: If it should happen that two different persons were invested with the imamate, that would be analogous to the situation of two guardians contracting a marriage for the same woman to two different suitors without either being aware of the other's contract. The decision in the matter rests on the application of jurisprudence. My opinion on this issue is that investiture of two individuals with the imamate in a single locality within relatively restricted boundaries and limited provinces is not permitted and the investiture should be in accord with a consensus. But, when the distances are great and the two Imams quite remote from each other, there is room to allow it, although this cannot be established conclusively.” 
The 11th century Sunni jurist Al-Mawardi wrote:
“The investment of two rulers in two different cities is invalid in both cases, for the ummah may not have two rulers simultaneously, even though there are some dissenting voices who would make that permissible. Jurists are disagreed regarding which one of the two should be sovereign. One party take him to be the one elected in the city where the previous leader died, because its residents are more entitled to make the choice, the rest of the Community in other districts delegating the task to them... Others have suggested that each one of the two must give up the office in favour of his opponent, thus allowing the elections to opt for one or the other..” 
Imam Al-Nawawi a 12th century authority of the Sunni Shafi'i madhhab said: "It is forbidden to give an oath to two caliphs or more, even in different parts of the world and even if they are far apart"
Imam Al-Juzairi, a more modern expert on the Fiqh of the four Sunni madhhabs said regarding the opinion of the four Imams, “...It is forbidden for Muslims to have two Imams in the world whether in agreement or discord." 
Several Arabic surnames found throughout the Middle East are derived from the word khalifa. These include: Khalif, Khalifa, Khillif, Kalif, Kalaf, Khalaf, and Kaylif. The usage of this title as a surname is comparable to the existence of surnames such as King, Duke, and Noble in the English language.
The more important dynasties include:
Note on the overlap of Umayyad and Abbasid Caliphates: After the massacre of the Umayyad clan by the Abbassids, one lone prince escaped and fled to North Africa, which remained loyal to the Umayyads. This was Abd-ar-rahman I. From there, he proceeded to Spain, where he overthrew and united the provinces conquered by previous Umayyad Caliphs (in 712 and 712). From 756 to 929, this Umayyad domain in Spain was an independent emirate, until Abd-ar-rahman III reclaimed the title of Caliph for his dynasty. The Umayyad Emirs of Spain are not listed in the summary below because they did not claim the caliphate until 929. For a full listing of all the Umayyad rulers in Spain see the Umayyad article.
Many local rulers throughout Islamic history have claimed to be caliphs. Most claims were ignored outside their limited domains. In many cases, these claims were made by rebels against established authorities and died when the rebellion was crushed. Notable claimants include:
“15:48, 7 October 2009 (UTC)15:48, 7 October 2009 (UTC)15:48, 7 October 2009 (UTC)~—…
CALIPH, Calif, or Khalif (Arab. khalifa; the lengthening of the a is strictly incorrect), literally "successor," "representative," a title borne originally by Abu Bekr, who, on the death of Mahomet, became the civil and religious head of the Mahommedan state. In the same sense the term is used in the Koran of both Adam and David as the vicegerents of God. Abu Bekr and his three (or four) immediate successors are known as the "perfect" caliphs; after them the title was borne by the thirteen Omayyad caliphs of Damascus, and subsequently by the thirty-seven Abbasid caliphs of Bagdad whose dynasty fell before the Turks in 1258. By some rigid Moslems these rulers were regarded as only amirs, not caliphs. There were titular caliphs of Abbasid descent in Egypt from that date till 1517 when the last caliph was captured by Selim I. On the fall of the Omayyad dynasty at Damascus, the title was assumed by the Spanish branch of the family who ruled in Spain at Cordova (75510 3 1), and the Fatimite rulers of Egypt, who pretended to descent from Ali, and Fatima, Mahomet's daughter, also assumed the name (see Fatimites).
According to the Shiite Moslems, who call the office the "imamate" or leadership, no caliph is legitimate unless he is a lineal descendant of the Prophet. The Sunnites insist that the office belongs to the tribe of Koreish (Quraish) to which Mahomet himself belonged, but this condition would vitiate the claim of the Turkish sultans, who have held the office since its transference by the last caliph to Selim I. According to a tradition falsely ascribed to Mahomet, there can be but one caliph at a time; should a second be set up, he must be killed, for he "is a rebel." (See MAHOMMEDAN INSTITUTIONS.)
caliph (plural caliphs)
Some of the early leaders of the Muslim community following Muhammad's (570–632) death called themselves "Khalifat Allah", meaning representative of God. But the other title of "Khalifat rasul Allah", meaning the successor to the prophet of God, became the common title. Some academics write the term as Khalīf.
Caliphs were often also called Amīr al-Mu'minīn (أمير المؤمنين), leader of the Muslims. This title has since been shortened to "emir". It is also found as a personal name in some countries.
After the first four caliphs (Abu Bakr, Umar ibn al-Khattab, Uthman ibn Affan, and Ali ibn Abi Talib), the title was used by the Umayyads, the Abbasids, and the Ottomans, as well as by other dynasties in Southern Pakistan, Spain, Northern Africa, and Egypt. Most historical Muslim rulers simply titled themselves sultans or amirs, and the caliph himself often had very little real authority. The title was not used after the Republic of Turkey abolished the Ottoman caliphate in 1924.