Ramadan is the ninth month of the Islamic calendar. It is observed by Muslims worldwide as a month of fasting (sawm), communal prayer (salah), reflection, and community. It is also the month in which the Quran is believed to have been revealed to the Islamic prophet Muhammad.

The annual observance of Ramadan is regarded as one of the Five Pillars of Islam and lasts twenty-nine to thirty days, from one sighting of the crescent moon to the next.

Fasting from dawn to sunset is obligatory (fard) for all adult Muslims who are not acutely or chronically ill, travelling, elderly, breastfeeding, pregnant, or menstruating. The predawn meal is referred to as suhoor, and the nightly feast that breaks the fast is called iftar.

Although rulings (fatawa) have been issued declaring that Muslims who live in regions with a midnight sun or polar night should follow the timetable of Mecca, it is common practice to follow the timetable of the closest country in which night can be distinguished from day.

The spiritual rewards (thawab) of fasting are believed to be multiplied during Ramadan. Accordingly, during the hours of fasting, Muslims refrain not only from food and drink, but also from all behavior deemed sinful in Islam, devoting themselves instead to prayer and study of the Quran.

Muslims hold that all scriptures were revealed during Ramadan — the scrolls of Abraham, the Torah, the Psalms, the Gospel, and the Quran — having been handed down during that month. Muhammad is said to have received his first Quranic revelation on Laylat al-Qadr, one of five odd-numbered nights that fall during the last ten days of Ramadan.

Although Muslims were first commanded to fast in the second year of Hijra (624 CE), they believe that fasting is not an innovation of monotheism, but rather has always been necessary for believers to attain fear of God (taqwa) [Quran 2:183]. They also note that the pre-Islamic pagans of Mecca fasted on the tenth day of Muharram to expiate sin and avoid drought.

Some scholars, such as Philip Jenkins, argue that the observance of Ramadan fasting grew out of "the strict Lenten discipline of the Syrian Churches," a view supported by theologian Paul-Gordon Chandler and others, but disputed by many Muslim academics. The Quran itself emphasizes that fasting had already been prescribed to earlier biblical communities (2:183), even though no explicit text describing this pre-Islamic practice exists.