Alawism (Arabic: علوية, romanized: ʿAlawiyya), also known as Nusayrism (Arabic: نصيرية, romanized: Nuṣayriyya), is an offshoot of early Shia Islam with influences from ancient Iranian, Christian, and Gnostic traditions. Its adherents, called the Alawites, are estimated to number around 4 million and are primarily concentrated in the Levant. Alawites venerate Ali ibn Abi Talib, the "first imam" in the Twelver school, as a manifestation of the divine essence. Fabrice Balanche wrote in 2024 that some core beliefs of the Alawites are rejected by orthodox theologians of Sunni and Shia Islam, with medieval scholar Ibn Taymiyyah calling for the sect to be eradicated. Balanche describes a lonely fatwa by Hajj Amin al-Husseini recognising them as Muslims, given in 1932 at a time when Alawites were denied this formal status, as based on immediate political, anticolonial considerations.

Alawite beliefs are centered in a divine Trinity, comprising three aspects of the one God, the ma'na (meaning), the ism (name), and the bab (door). These emanations are understood to have undergone reincarnation cyclically seven times in human form throughout history, the last seventh incarnation being that of Ali, Muhammad and Salman the Persian. Alawite practices include consecration of wine in the form of Mass, entombing the deceased in sarcophagi, observing cultural holidays such as Akitu, Christmas, Nowruz, Mawlid and Gazwela.

Alawism originated in 9th-century Iraq as a ghulat sect that separated from Shia Islam led by Ibn Nusayr, a preacher from the aristocratic Banu Numayr clan. The Alawites were organized in Aleppo during Hamdanid rule in Syria by al-Khasibi, a missionary who had gained patronage from Emir Sayf al-Dawla (r. 945–967). In the 11th–12th-century, the Alawite community were budded to the Syrian Coastal Mountain Range with the help of the Banu Muhriz. Later, the Alawites faced severe persecution by waves of the Crusaders, Mamluks, and by Ottoman conquerors. In the aftermath of the First World War, the Alawite State was established in coastal Syria. Although the state was later dismantled, Alawite figures continued to play a pivotal role in the Syrian military and later in the Ba'ath Party. The Corrective Movement of 1970 led by Hafez al-Assad, an Alawite, resulted in an establishment of an Alawite-led establishment that continued under his son Bashar al-Assad, who was eventually overthrown during the Syrian civil war.

Alawism is one of the main religious groups in the Middle East, with over 4 million followers. They are primarily located in Lebanon, Syria, and Turkey. Alawism is the third largest-religion in Syria, accounting for 10% of the country. As the only ghulat sect alive, it faces persecution by Islamist extremists.

The term Alawite is derived from the Arabic word Alawi, denoting the "followers of Ali". The community historically self-identified as Nusayrites, named after their religious founder Ibn Nusayr. However, the term "Nusayri" had fallen out of currency by the 1920s, as a movement led by intellectuals within the community during the French mandate sought to replace it with "Alawite". The term "Nusayrites" is now sometimes considered a religious slur. Another term applied to the group was Ansari, which, according to Samuel Lyde, was a term that the mid-19th-century Alawites used among themselves. However, others indicate that Ansari is simply a Western error in the transliteration of Nusayri.

The French were known to have popularised the term Alawite. The community also characterised the older name (which implied "a separate ethnic and religious identity") as an "invention of the sect's enemies", ostensibly favouring an emphasis on "connection with mainstream Islam"—particularly the Shia branch. As such, "Nusayrite" is now regarded as antiquated, and has even come to have insulting and abusive connotations. The term was frequently employed as hate speech by Sunni fundamentalists fighting against Bashar al-Assad's government in the Syrian civil war, who use its emphasis on Ibn Nusayr to insinuate that Alawi beliefs are "man-made" and not divinely inspired. Necati Alkan argued in an article that the "Alawi" appellation was used in an 11th-century Nusayri book and was not a 20th-century invention. The following quote from the same article illustrates his point:

"As to the change from "Nuṣayrī" to "ʿAlawī": most studies agree that the term "ʿAlawī" was not used until after WWI and probably coined and circulated by Muḥammad Amīn Ghālib al-Ṭawīl, an Ottoman official and writer of the famous Taʾrīkh al-ʿAlawiyyīn (1924). However, the name 'Alawī' appears in an 11th-century Nuṣayrī tract as one of the names of the believer (...). Moreover, the term 'Alawī' was already used at the beginning of the 20th century. In 1903 the Belgian-born Jesuit and Orientalist Henri Lammens (d. 1937) visited a certain Ḥaydarī-Nuṣayrī sheikh Abdullah in a village near Antakya and mentions that the latter preferred the name 'Alawī' for his people. Lastly, it is interesting to note that in the above-mentioned petitions of 1892 and 1909 the Nuṣayrīs called themselves the 'Arab Alawī people' (ʿArab ʿAlevī ṭāʾifesi) 'our ʿAlawī Nuṣayrī people' (ṭāʾifatunā al-Nuṣayriyya al-ʿAlawiyya) or 'signed with Alawī people' (ʿAlevī ṭāʾifesi imżāsıyla). This early self-designation is, in my opinion, of triple importance. Firstly, it shows that the word 'Alawī' was always used by these people, as ʿAlawī authors emphasize; secondly, it hints at the reformation of the Nuṣayrīs, launched by some of their sheikhs in the 19th century and their attempt to be accepted as part of Islam; and thirdly, it challenges the claims that the change of the identity and name from 'Nuṣayrī' to 'ʿAlawī' took place around 1920, in the beginning of the French mandate in Syria (1919–1938)."

The Alawites are distinct from the Alevi sect in Turkey, although the terms share a common etymology and pronunciation. To avoid confusion with the ethnic Turkish and Kurdish Alevis, the Alawites call themselves Arap Alevileri ("Arab Alevis") in Turkish. The term Nusayrī, previously used in theological texts, has been revived in recent studies. A quasi-official name used during the 1930s by Turkish authorities was Eti Türkleri ("Hittite Turks"), to conceal their Arabic origins. Although this term is obsolete, it is still used by some older people as a euphemism.