Islam is unambiguously monotheistic — in fact, the belief in one God, called tawhid in Arabic, is considered the single most fundamental principle in the entire religion, more central than any other teaching or practice. Understanding why this question even comes up, and how strictly Islam enforces it, helps clarify one of the religion's core distinctions.
The word "Islam" itself relates to submission to God, and the very first pillar of the religion — the Shahada — is a direct statement of monotheism: "La ilaha illallah," meaning "there is no god but Allah." This declaration isn't just an opening formality; it's repeated in daily prayers, whispered to newborns, and recited at the moment of death, making the assertion of one God the thread running through nearly every major moment of a Muslim's life.
Surah Al-Ikhlas, a short but heavily emphasized chapter of the Quran, exists almost entirely to define this concept: "Say: He is Allah, the One. Allah, the Eternal Refuge. He neither begets nor is born, nor is there to Him any equivalent." Despite being only four verses, a hadith describes this surah as equal in reward to one-third of the entire Quran, reflecting how central its message of pure monotheism is considered to be.
Islam takes this principle further than simply affirming one God exists — it actively identifies and warns against shirk, the sin of associating partners with Allah, whether through worshipping other beings, believing other entities share His powers, or attributing divine qualities to anyone or anything else. The Quran describes shirk as the one sin Allah does not forgive if a person dies upon it without repentance, underscoring how seriously monotheism is treated — not as one belief among many, but as the non-negotiable foundation on which everything else in Islamic belief and practice rests.
This is also where Islam draws firm lines with certain beliefs in other Abrahamic traditions. While Islam recognizes Isa (Jesus) as a prophet and messenger, it explicitly rejects the concept of the Trinity and Jesus's divine sonship, viewing these as forms of shirk that compromise strict monotheism. Surah Maryam and Surah Al-Ikhlas both directly address this, making clear that Allah has no partners, no equals, and no offspring.
Historically, pre-Islamic Arabia was largely polytheistic, with the Kaaba in Mecca reportedly housing hundreds of idols representing different deities before Prophet Muhammad's mission. Islam's arrival represented a direct confrontation with this polytheistic system, and much of the Quran's early Meccan revelation focuses heavily on establishing and defending tawhid against the surrounding polytheistic culture — context that helps explain why monotheism receives such intense, repeated emphasis throughout the Quran rather than being stated once and left aside.
So to directly answer the question: Islam is monotheistic, and this isn't a minor theological detail but the defining, non-negotiable core of the entire religion, woven into its central declaration of faith, its daily prayers, and one of its most-recited chapters.
It's worth noting that this strict monotheism is also why Islam places such emphasis on avoiding intermediaries in worship — praying directly to Allah without saints, statues, or other figures acting as go-betweens. This is another practical expression of tawhid: not only affirming one God in belief, but structuring worship itself so that no other being, however respected, becomes an object of veneration alongside Him.