Monotheism in pre-Islamic Arabia refers to the belief in a supreme Creator being among inhabitants of the Arabian peninsula. This practice could be found among pre-Islamic Christian, Jewish, and other populations unaffiliated with either one of the two Abrahamic religions at the time. Monotheism became a widespread religious trend in pre-Islamic Arabia in the fourth century, when it began to quickly supplant the polytheism that had been the common form of religion until then.^[1] The transition from polytheism to monotheism in this time is documented from inscriptions in all writing systems on the Arabian Peninsula (including those in Nabataean, Safaitic, and Sabaic), where polytheistic gods and idols cease to be mentioned. Epigraphic evidence is nearly exclusively monotheistic in the fifth century,^[2] and from the sixth century and until the eve of Islam, it is solely monotheistic.^[3] Pre-Islamic Arabic poetry is also monotheistic or henotheistic.^[4]

An important locus of pre-Islamic Arabian monotheism was in the Himyarite Kingdom that ruled over South Arabia, whose ruling class converted to Judaism in the fourth century (roughly when official polytheistic inscriptions stop appearing in the area) who nevertheless present a neutral outwards monotheism in engagement with the public. This monotheism that came to be prevalent among populations unaffiliated with either Abrahamic religion has been called by many terms by historians, including "gentile monotheism," "pagan monotheism," "Himyarite monotheism," "Arabian monotheism," "hanifism," "Rahmanism," and so on.^[5] In the sixth century, the Aksumite invasion of Himyar leads to Christian rule in the region.

Early attestations of Arabian polytheism include Esarhaddon's Annals, mentioning Atarsamain, Nukhay, Ruldaiu, and Atarquruma. Herodotus, writing in his Histories, reported that the Arabs worshipped Orotalt (identified with Dionysus) and Alilat (identified with Aphrodite).^[6] Strabo stated the Arabs worshipped Dionysus and Zeus. Origen stated they worshipped Dionysus and Urania.^[6] Similarly, late Nabataean, Safaitic, and Sabaic inscriptions attest to the veneration of a broad array of sacred stones and polytheistic deities until the fourth century.^[5]

The first Roman emperor to convert to Christianity was Constantine the Great. The first recorded attempt to convert a region of Arabia into monotheistic faith is attributed to Constantius II, his successor. According to the Greek historian Philostorgius (d. 439) in his Ecclesiastical History 3.4, Constantius sent an Arian bishop known as Theophilus the Indian (also known as "Theophilus of Yemen") to Tharan Yuhanim, then the king of the South Arabian Himyarite Kingdom to convert the people to Christianity. According to the report, Theophilus succeeded in establishing three churches, one of them in the capital Zafar.^[7] However, Tharan did not convert to Christianity. Several decades later, the ruling class of the Himyarite Kingdom would convert to Judaism during the reign of Malkikarib Yuhamin, potentially motivated by a wish to distance themselves from the Byzantine Empire.^[8] It is in the mid-fourth century that inscriptions suddenly transition from polytheistic invocations to ones mentioning the high god Rahmanan (whose name means "The Merciful One").^[9] A Sabaic inscription dating to this time, titled Ja 856 (or Fa 60) describes the replacement of a polytheistic temple dedicated to the god al-Maqah with a mikrāb (which might be the equivalent of a synagogue or an original form of organization local to Himyarite Judaism^[10]). The evidence suggests a sharp break with polytheism, coinciding with the sudden appearance of Jewish and Aramaic words (‘ālam/world, baraka/bless, haymanōt/guarantee, kanīsat/meeting hall) and personal names (Yṣḥq/Isaac, Yhwd’/Juda), Yws’f/Joseph).^[8]

Soon after and prompted by the massacre of the Christian community of Najran during the reign of the militant Jewish ruler Dhu Nuwas in the early sixth century, the Kingdom of Aksum in Ethiopia would invade, leading to an ousting of Jewish leadership over the region.^[11] Sumyafa Ashwa came into power, but he was soon overthrown by his rival Abraha, initiating a period of Ethiopian Christian rule over southern Arabia in 530.^[12] During the Ethiopian Christian period, Christianity appears to have become the official religion.^[13] Many churches began to be built.^[14] For example, the inscription RIÉ 191, discovered in Axum, describes the construction of a church off the coast of Yemen. The Marib Dam inscription from 548 mentions a priest, a monastery, and an abbot of that monastery.^[15] As in the Himyarite period, Christian inscriptions continue to refer to the monotheistic deity using the name Rahmanan, but now these inscriptions are accompanied with crosses and references to Christ as the Messiah and the Holy Spirit. For example, one (damaged) inscription, as for example in Ist 7608 bis. Another extensive inscription, CIH 541, documents Abraha sponsoring the construction of a church at Marib, besides invoking/mentioning the Messiah, Spirit, and celebrations hosted by a priest at another church. Later Islamic historiography also ascribes to Abraha the construction of a church at Sanaa. Abraha's inscriptions bear a relatively low Christology, perhaps meant to assuage the Jewish population, and their formulae resemble descriptions of Jesus in the Quran.^[16] (The Jabal Dabub inscription is another South Arabian Christian graffito dating to the sixth century and containing a pre-Islamic variant of the Basmala.^[17]) Whereas Abraha's predecessor more explicitly denoted Jesus as the Son of Rahmanan and as "Victor" (corresponding to Aksumite description under Kaleb of Axum), and made use of Trinitarian formulae, Abraha began to only describe Jesus as God's "Messiah" (but not Son) and, in aligning himself more closely with Syriac Christianity, replaced Aksumite Christian with Syriac loanwords. More broadly, the separation of Abraha's Himyar from the Akumsite kingdom corresponded to its greater alignment with the Christianity espoused in Antioch and Syria. Inscriptions from this region disappear after 560.^[13] Abraha's influence would end up extending across the regions he conquered, including regions of eastern Arabia, central Arabia, Medina in the Hejaz, and an unidentified site called Gzm.^[18]

With a few exceptions, all inscriptions from the fourth to sixth centuries are not polytheistic:^[19] among over one hundred monumental inscriptions that could testify to a polytheistic cult, only two of them do, along with less than ten inscriptions from wood remains.^[20] Similarly, of 58 extant Late Sabaic inscriptions that mention the theonym Rahmanan from the period of Jewish rule in south Arabia, none of them can be labelled as pagan or polytheistic. Invocation of alternative deities was rare, though it suggests the cult surrounding Rahmanan was henotheistic as opposed to purely monotheistic. Once Christian rule initiates in South Arabia in the early sixth century, extant inscriptions become purely monotheistic.^[21]

Epigraphic evidence further attests to the spread of Judaism beyond South Arabia, into northwestern Arabia,^[22][23] as well as Christianity into all major regions of Arabia^[2] including northern Arabia and the southern Levant, southern Arabia, western Arabia,^[24] and across the gulf of eastern Arabia.^[25][26] All Paleo-Arabic inscriptions from the fifth and sixth centuries, which have been found in all major regions of the Arabian peninsula and in the southern Levant, are either monotheistic or explicitly Christian.^[27] These inscriptions also demonstrate a penetration of monotheism into previously thought holdouts or surviving bastions of paganism or polytheism, such as Dumat al-Jandal and Taif (which ibn al-Kalbi held to be the centre of the cult of Al-Lat in the sixth century).^[27] These inscriptions refer to God with the use of terms like Allāh, al-Ilāh (ʾl-ʾlh), and Rabb ("Lord"). The uncontracted form Al-Ilāh/ʾl-ʾlh is thought to have among Christians as an isomorphism or calque for the Greek expression ho theos, which is how the Hebrew ʾĕlōhîm is rendered in the Septuagint.^[28] This uncontracted form continued to be used by Christians until the tenth century, even as the form ʾllh appeared in the Quran with two consecutive lāms without a hamza.^[29] One Islamic-era example of the uncontracted form is in the Yazid inscription.^[30]

Muslim-era historiographical sources, such as the eighth-century Book of Idols by Hisham ibn al-Kalbi as well as the writings of the Yemeni historian al-Hasan al-Hamdani on South Arabian religious beliefs continue to depict pre-Islamic Arabia as dominated by polytheistic practices until the sudden rupture brought about by the coming of Muhammad and his career between 610 and 632.^[31] However, Islamic-era compilations of pre-Islamic poetry only sporadically describe idols or polytheistic practice and principally evince monotheistic or henotheistic beliefs.^[32][33] The Quran may also occasionally refer to vestiges of polytheistic deities in two separate verses, but its better-attested descriptions of the "associators" (mushrikūn) have been increasingly understood, since originally being posited by Julius Wellhausen, to be references to monotheistic/henotheistic individuals who did not dispute the supremacy of Allah but instead believed in other beings (such as angels) that acted as intermediaries in the devotion to the one high God.^[34][35][36]

Ibn Hazm (d. 1064) attempts to describe the broad landscape of pre-Islamic religious belief in his Jamharat ansāb al-ʿArab (Compilation of Arab Genealogy):^[37]

all of [Mesopotamian tribes] Iyād and Rabīʿah and Bakr and Taghlib and Namar and [the eastern] ʿAbd al-Qays are Christian, so too is [Syrian] Ghassān, and [the southern] Banū Ḥārith ibn Kaʿb in Najrān, and [the northern] al-Ṭayyiʾ, Tanūkh, many of [the Syrian] Kalb, and all those from [Najdi] Tamīm and [Iraqi] Lakhm residing in Ḥīrah. Ḥimyar were Jewish, as were many from Kindah. Khathʿam had no religion at all (lā tadīn bi-shayʾ aṣlan). Zoroastrianism (al-majūsiyyah) appeared among Tamīm, and it is said that Laqīṭ ibn Zurārah had converted to Zoroastrianism (qad tamajassa). The rest of the Arabs worshipped idols.

• Christianity in pre-Islamic Arabia
• Hypsistarians

• Sinai, Nicolai (2019). Rain-giver, bone-breaker, score-settler: allāh in Pre-Quranic poetry. Lockwood Press.

• Zoroastrianism in Arabia (Ancient Arabia Database)