Allah (Arabic: اﷲ, Allāh) is the standard Arabic word for "God", derived from al-ilah, the God. The term is best known in the West for its use by Muslims as a reference to God. Arabic-speakers of all faiths, including Christians and Jews, use the word "Allah" to mean "God". The Muslim and Christian Arabs of today have no other word for 'God' than 'Allah'. In pre-Islamic Arabia, Allah was used by pagan Meccans as a reference to the creator-god, possibly the supreme deity.

In Islam, Allah is the only Deity, Transcendent Creator of the universe, and the Judge of humankind . Some Islamic scholars believe that the term "Allāh" should not be translated, arguing that "Allāh" as used in Islam is a special and glorified term whose use should be preserved, while God can also be used in reference to deities worshiped by polytheists.

The most likely theory regarding the etymology of the term "Allāh" (اﷲ) is that it is derived from a contraction of the Arabic words al- (the) and ʾilāh (deity, masculine form) to al-lāh meaning "the God". Cognates of the name "Allāh" exist in other Semitic languages, including Hebrew and Aramaic. The corresponding Aramaic form is ’Ĕlāh, in Biblical Aramaic, and ’Allāhā, in Syriac.

Synchronically, the term Allah does not have a plural form or a feminine gender in the Arabic language. The historical (pre-Islamic) corresponding feminine is Allāt.

Regardless of etymology, the synchronic Muslim understanding of the term does not consider it as a proper name like any other, but rather as the "name of the nameless God, next to whom there is no other."

The pre-Islamic Arabs believed in a host of other terms to signify gods, such as Hubal, al-Lāt, al-`Uzzah and Manah. Pre-Islamic Jews referred to their supreme creator as Yahweh or Elohim. This view of Allāh by the pre-Islamic pagans is viewed by Muslims as a later development having arisen as a result of moving away from Abrahamic monotheism over time since the building of the Ka'ba. The Qur'an transmits a rebuttal to this common belief at the time in the verse [Qur'an 17:40]: "Has then your Lord (O Pagans!) preferred for you sons, and taken for Himself daughters among the angels? Truly ye utter a most dreadful saying!". Secular historians, meanwhile, have postulated that monotheism is the result of an evolution from henotheism, the belief in a supreme deity as well as various lesser divinities. The pagan Arabians also used the word "Allāh" in the names of their children; Muhammad's father, who was born into pagan society, was named "Abdullāh", which translates "servant of Allāh". "Abdullāh" is still used for names of Muslims and non-Muslims (e.g. Christians also used the word, as testified by the Zabad inscription).

The Hebrew word for deity, El (אל) or Elōah (אלוה), was used as a Tanakh synonym for Tetragrammaton (יהוה), which is the proper name of God according to the Hebrew Bible. The Aramaic word for God is alôh-ô (Syriac dialect) or elâhâ (Biblical dialect), which comes from the same Proto-Semitic word (*'ilâh-) as the Arabic and Hebrew terms; Jesus is described in Mark 15:34 as having used the word on the cross, with the ending meaning "my", when saying, "My God, my God, why hast thou forsaken me?" (transliterated in Greek as elō-i).

One of the earliest surviving translations of the word Allāh into a foreign language is in a Greek translation of the Shahada, from 86-96 AH (705-715 AD), which translates it as ho theos monos, literally "the one god". Also the cognate Aramaic term appears in the Aramaic version of the New Testament, called the Pshitta (or Peshitta) as one of the words Jesus used to refer to God, e.g., in the sixth Beatitude, "Blessed are the pure in heart for they shall see Alaha."

Most Arabic-speaking Christian and Jewish Communities (including the Yemenite Jews, several Mizrahi communities and some Sephardim), as well as Eastern Christians living in Muslim countries (such as Orthodox Christians in Turkey), use "Allāh" as the proper noun for "God". The name's origin can be traced back to the earliest Semitic writings in which the word for god was Il or El, the latter being an Old Testament synonym for Yahweh. Allah is the standard Arabic word for "God" and is used by Arab Christians as well.

Because of the centuries long Muslim presence in the Iberian Peninsula, the words ojalá and oxalá today exist in the Spanish and Portuguese languages, respectively, borrowed from Arabic by way of Mozarabic. These words literally mean "God willing" (in the sense of "I hope so").

The word 'Allah' in the Indonesian language, means God, it is used alternatively with the word "Tuhan". Indonesia recognises six religions (Islam (majority), Protestantism, Roman Catholicism, Hinduism, Buddhism, and Confucianism), all of which use these two words to refer to God or gods. However, religions other than Islam, use a different pronunciation for "Allah," although the spelling is the same