Denominations

Various Denominations in Islam

Sunni Islam

Sahih Al-Bukhari, one of the six Sunni hadith books.
The largest denomination in Islam is Sunni Islam, which makes up 75%–90% of all Muslims and is arguably the world's largest religious denomination. Sunni Muslims also go by the name Ahl as-Sunnah which means "people of the tradition [of Muhammad"] These hadiths, recounting Muhammad's words, actions, and personal characteristics, are preserved in traditions known as Al-Kutub Al-Sittah (six major books).

Sunnis believe that the first four caliphs were the rightful successors to Muhammad; since God did not specify any particular leaders to succeed him and those leaders were elected. Sunnis believe that anyone who is righteous and just could be a caliph but they have to act according to the Quran and the Hadith, the example of Muhammad and give the people their rights.

The Sunnis follow the Quran, then the Hadith. Then for legal matters not found in the Quran or the Hadith, they follow four madh'habs (schools of thought): Hanafi, Hanbali, Maliki and Shafi'i, established around the teachings of Abū Ḥanīfa, Ahmad bin Hanbal, Malik ibn Anas and al-Shafi'i respectively. All four accept the validity of the others and a Muslim may choose any one that he or she finds agreeable. Ahl al-Hadith is a movement that deemphasized sources of jurisprudence outside the quran and sunnah, such as informed opinion (ra'y).

The Salafi movement claim to take the first three generations of Muslims, known as the salaf, as exemplary models. In the 18th century, Muhammad ibn Abd al-Wahhab led a salafi movement, referred by outsiders as Wahhabism, in modern-day Saudi Arabia.

The Barelvi movement, a revivalist movement of Sunni Islam with over 200 million followers, emerged as part of debate of how to redeem India from the British. The movement emphasizes primacy of Islamic law in all matters with adherence to Sufi practices and personal devotion to Muhammad and has addressed leading issues for Muslims since partition. The Deobandi movement is an Indo-Pakistani reformist movement that is much influenced by the Wahhabi movement. The Barelvi and Deobandi movements of Sunni Islam accept the validity of all four Sunni madh'habs.

Shia Islam

The Imam Hussein Shrine in Karbala, Iraq is a holy site for Shia Muslims.

The Shia constitute 10–20% of Islam and are its second-largest branch.

While the Sunnis believe that a Caliph should be elected by the community, Shia's believe that Muhammad appointed his son-in-law, Ali ibn Abi Talib, as his successor and only certain descendants of Ali could be Imams. As a result, they believe that Ali ibn Abi Talib was the first Imam (leader), rejecting the legitimacy of the previous Muslim caliphs Abu Bakr, Uthman ibn al-Affan and Umar ibn al-Khattab. Another point of contention is the cursing of figures revered by Sunnis. However, Jafar al-Sadiq himself disapproved of people who disapproved of his great grand father Abu Bakr and Zayd ibn Ali revered Abu Bakr and Umar. More recently, Grand Ayatollah Ali al-Sistani condemned the practice.

Shia Islam has several branches, the most prominent being the Twelvers (the largest branch), Zaidis and Ismailis. Different branches accept different descendants of Ali as Imams. After the death of Imam Jafar al-Sadiq who is considered the sixth Imam by the Twelvers and the Ismaili's, the Ismailis recognized his son Isma'il ibn Jafar as his successor whereas the Twelver Shia's (Ithna Asheri) followed his other son Musa al-Kadhim as the seventh Imam. The Zaydis consider Zayd ibn Ali, the uncle of Imam Jafar al-Sadiq, as their fifth Imam, and follow a different line of succession after him.

Other smaller groups include the Bohra as well as the Alawites and Alevi. Some Shia branches label other Shia branches that do not agree with their doctrine as Ghulat.

Sufism

Sufism, or tasawwuf (Arabic: تصوف‎‎), is a mystical-ascetic approach to Islam that seeks to find a direct personal experience of God. It is not a sect of Islam and its adherents belong to the various Muslim denominations. Classical Sufi scholars have focused on the reparation of the heart and turning it away from all else but God by making use of "intuitive and emotional faculties" that one must be trained to use. Hasan al-Basri was inspired by the ideas of piety and condemnation of worldliness preached by Muhammad and these ideas were later further developed by Al-Ghazali. Traditional Sufis, such as Bayazid Bastami, Jalaluddin Rumi, Haji Bektash Veli, Junaid Baghdadi, and Al-Ghazali, argued for Sufism being based upon the tenets of Islam and the teachings of Muhammad.

Sufism enjoyed a strong revival in central Asia and South Asia. Central Asia is considered to be a center of Sufism. Sufism has played a significant role in fighting against Tsars of Russia and Soviet colonization. Here, Sufis and their different orders are the main religious sources. Sufism is also strong in African countries such as Tunisia, Algeria, Morocco, Senegal, Chad and Niger.

Sufi practices such as veneration of saints have faced stiff opposition from followers of Salafism and Wahhabism, who have sometimes physically attacked Sufi places of worship, leading to deterioration in Sufi–Salafi relations.

Other denominations
Ahmadiyya is an Islamic reform movement (with Sunni roots) founded by Mirza Ghulam Ahmad that began in India in 1889 and is practiced by 10 to 20 million Muslims around the world. Ahmad claimed to have fulfilled the prophecies concerning the arrival of the 'Imam Mahdi' and the 'Promised Messiah'.

The Ibadi is a sect that dates back to the early days of Islam and is a branch of Kharijite and is practiced by 1.45 million Muslims around the world. Unlike most Kharijite groups, Ibadism does not regard sinful Muslims as unbelievers.

Mahdavia is an Islamic sect that believes in a 15th-century Mahdi, Muhammad Jaunpuri
The Quranists are Muslims who generally reject the Hadith.
Yazdânism is seen as a blend of local Kurdish beliefs and Islamic Sufi doctrine introduced to Kurdistan by Sheikh Adi ibn Musafir in the 12th century.
There are also black Muslim movements such as the Nation of Islam (NOI), Five-Percent Nation and Moorish scientists.