The Qur'an is the sacred book of Islam. It has also been called, in English, "the Koran" and "the Qur’an". Qur'an is the currently preferred English transliteration of the Arabic original (قرآن); it means “recitation”. Although it is referred to as a "book", when a Muslim refers to the Qur'an, they are referring to the actual text, the words, rather than the printed work itself.

Muslims believe that the Qur'an was revealed to the Prophet Muhammad by the Angel Gabriel on numerous occasions between the years and Muhammad's death in 632. In addition to memorizing his revelations, his followers are said to have written them down on parchments, stones, and other media, so that the entire Qur'an was written down during the lifetime of Prophet Muhammad. Muslims believe that the Qur'an had been written in its entirety by God long before the creation of the Universe and that it was sent down in its entire form to the highest point of the universe (Siddratul Muntaha). Thereafter, relevant portions of the Quran was then brought down bit by bit to the earth to Prophet Muhammad by Gabriel at various points in time according to episodes in the Prophet's life in a series of divine revelations (the wahyu).

Muslims hold that the Qur'an available today is the same as that revealed to Prophet Muhammad and by him to his followers, who memorized his words. Scholars generally accept that the version of the Qur'an used today was first compiled in writing by the third Caliph, Uthman ibn Affan, sometime between 650 and 656. He sent copies of his version to the various provinces of the new Muslim empire, and directed that all variant copies be destroyed. However, some skeptics doubt the recorded oral traditions (hadith) on which the account is based and will say only that the Qur'an must have been compiled before 750.

There are also numerous traditions, and many conflicting academic theories, as to the provenance of the verses later assembled into the Qur'an (This is covered in greater detail in the article on the Qur'an). Most Muslims accept the account recorded in several hadith, which state that Abu Bakr, the first caliph, ordered Zayd ibn Thabit to collect and record all the authentic verses of the Qur'an, as preserved in written form or oral tradition. Zayd's written collection, privately treasured by Muhammad's widow Hafsa bint Umar, was used by Uthman and is the basis of today's Qur'an.

Uthman's version organized the suras roughly in order of length, with the longest suras at the start of the Qur'an and the shortest ones at the end. More conservative views state that the order of most suras was divinely set. Later scholars have struggled to put the suras in chronological order, and among Muslim commentators, at least there is a rough consensus as to which suras were revealed in Mecca and which at Medina. Some suras (e.g. surat Iqra) are thought to have been revealed in parts at separate times.

Because the Qur'an was first written (date uncertain) in the Hijazi, Mashq, Ma'il, and Kufic scripts, which write consonants only and do not supply the vowels, and because there were differing oral traditions of recitation, as non-native Arabic speakers converted to Islam, there was some disagreement as to the exact reading of many verses. Eventually, scripts were developed that used diacritical markings (known as points) to indicate vowels. For hundreds of years after Uthman's recension, Muslim scholars argued as to the correct pointing and reading of Uthman's unpointed official text, (the rasm). Eventually, most commentators accepted seven variant readings (qira'at) of the Qur'an as canonical, while agreeing that the differences are minor and do not affect the meaning of the text.

The form of the Qur'an most used today is the Al-Azhar text of 1923, prepared by a committee at the prestigious Cairo university of Al-Azhar.

The Qur'an early became a focus of Muslim devotion and eventually a subject of theological controversy among skeptics. In the 8th century, the Mu'tazilis claimed that the Qur'an was created in time and was not eternal. Their opponents, of various schools, claimed that the Qur'an was eternal and perfect, existing in heaven before it was revealed to Muhammad. The Ashari theology (which ultimately became predominant) held that the Qur'an was uncreated.

Most Muslims regard paper copies of the Qur'an with extreme veneration, wrapping them in a clean cloth, keeping them on a high shelf, and washing as for prayers before reading the Qur'an. Old Qur'ans are not destroyed as wastepaper, but burned or deposited in Qur'an graveyards.

Most Muslims memorize at least some portion of the Qur'an in the original language. Those who have memorized the entire Qur'an are known as hafiz. This is not a rare achievement; it is believed that there are millions of hafiz today including many children.

From the beginning of the faith, most Muslims believed that the Qur'an was perfect only as revealed in Arabic. Translations were the result of human effort and human fallibility, as well as lacking the inspired poetry believers find in the Qur'an. Translations are therefore only commentaries on the Qur'an, or "translations of its meaning", not the Qur'an itself. Many modern, printed versions of the Qur'an feature the Arabic text on one page, and a vernacular translation on the facing page.