The Hijri calendar (Arabic: ٱلتَّقْوِيم ٱلْهِجْرِيّ at-taqwīm al-hijrīy), also known as the Lunar Hijri calendar and (in English) as the Islamic, Muslim or Arabic calendar, is a lunar calendar consisting of 12 lunar months in a year of 354 or 355 days. It is used to determine the proper days of Islamic holidays and rituals, such as the annual period of fasting and the proper time for the Hajj. In almost all countries where the predominant religion is Islam, the civil calendar is the Gregorian calendar, with Syriac month-names used in the Levant and Mesopotamia (Iraq, Syria, Jordan, Lebanon and Palestine) but the religious calendar is the Hijri one.

This calendar enumerates the Hijri era, whose epoch was established as the Islamic New Year in 622 CE. During that year, Muhammad and his followers migrated from Mecca to Medina and established the first Muslim community (ummah), an event commemorated as the Hijrah. In the West, dates in this era are usually denoted AH (Latin: Anno Hegirae, "in the year of the Hijrah"). In Muslim countries, it is also sometimes denoted as H from its Arabic form (سَنَة هِجْرِيَّة, abbreviated ھ). In English, years prior to the Hijra are denoted as BH ("Before the Hijra").As of 10 August 2021 CE, the current Islamic year is 1443 AH. In the Gregorian calendar reckoning, 1443 AH runs from approximately 10 August 2021 to 28 July 2022.