Al-Aqsa (/æl ˈæksə/; Arabic: الأَقْصَى, romanized: Al-Aqṣā) or al-Masjid al-Aqṣā (Arabic: المسجد الأقصى) is the compound of Islamic religious buildings that sit atop the Temple Mount, also known as the Haram al-Sharif, in the Old City of Jerusalem, including the Dome of the Rock, many mosques and prayer halls, madrasas, zawiyas, khalwas and other domes and religious structures, as well as the four encircling minarets. It is considered the third holiest site in Islam. The compound's main congregational mosque or prayer hall is variously known as Al-Aqsa Mosque, Qibli Mosque or al-Jāmiʿ al-Aqṣā, while in some sources it is also known as al-Masjid al-Aqṣā; the wider compound is sometimes known as Al-Aqsa Mosque compound in order to avoid confusion.

During the rule of the Rashidun caliph Umar (r. 634–644) or the Umayyad caliph Mu'awiya I (r. 661–680), a small prayer house on the compound was erected near the mosque's site. The present-day mosque, located on the south wall of the compound, was originally built by the fifth Umayyad caliph Abd al-Malik (r. 685–705) or his successor al-Walid I (r. 705–715) (or both) as a congregational mosque on the same axis as the Dome of the Rock, a commemorative Islamic monument. After being destroyed in an earthquake in 746, the mosque was rebuilt in 758 by the Abbasid caliph al-Mansur (r. 754–775). It was further expanded upon in 780 by the Abbasid caliph al-Mahdi (r. 775–785), after which it consisted of fifteen aisles and a central dome. However, it was again destroyed during the 1033 Jordan Rift Valley earthquake. The mosque was rebuilt by the Fatimid caliph al-Zahir (r. 1021–1036), who reduced it to seven aisles but adorned its interior with an elaborate central archway covered in vegetal mosaics; the current structure preserves the 11th-century outline.

During the periodic renovations undertaken, the ruling Islamic dynasties constructed additions to the mosque and its precincts, such as its dome, façade, minarets, and minbar and interior structure. Upon its capture by the Crusaders in 1099, the mosque was used as a palace; it was also the headquarters of the religious order of the Knights Templar. After the area was conquered by Saladin (r. 1174–1193) in 1187, the structure's function as a mosque was restored. More renovations, repairs, and expansion projects were undertaken in later centuries by the Ayyubids, the Mamluks, the Ottomans, the Supreme Muslim Council of British Palestine, and during the Jordanian annexation of the West Bank. Since the beginning of the ongoing Israeli occupation of the West Bank, the mosque has remained under the independent administration of the Jerusalem Waqf.

Al-Aqsa holds high geopolitical significance due to its location atop the Temple Mount, in close proximity to other historical and holy sites in Judaism, Christianity and Islam, and has been a primary flashpoint in the Israeli–Palestinian conflict.

The English term "Al-Aqsa Mosque" is the translation of both al-Masjid al-Aqṣā (ٱلْمَسْجِد ٱلْأَقْصَىٰ) and Jāmiʿ al-Aqṣā (جَامِع ٱلْأَقْصَىٰ), which have distinct Islamic meanings in Arabic. The former (al-Masjid al-Aqṣā) refers to the Quran's Surah 17 – "the farthest mosque" – traditionally refers to the entirety of the Temple Mount compound, while the latter name (Jāmiʿ al-Aqṣā) is used specifically for the silver-domed congregational mosque building. Arabic and Persian writers such as 10th-century geographer al-Muqaddasi, 11th-century scholar Nasir Khusraw, 12th-century geographer al-Idrisi and 15th-century Islamic scholar Mujir al-Din, as well as 19th-century American and British Orientalists Edward Robinson, Guy Le Strange and Edward Henry Palmer explained that the term Masjid al-Aqsa refers to the entire esplanade plaza also known as the Temple Mount or Haram al-Sharif ('Noble Sanctuary') – i.e. the entire area including the Dome of the Rock, the fountains, the gates, and the four minarets – because none of these buildings existed at the time the Quran was written. Al-Muqaddasi referred to the southern building (the subject of this article) as Al Mughattâ ("the covered-part") and Nasir Khusraw referred to it with the Persian word Pushish (also the "covered part," exactly as "Al Mughatta") or the Maqsurah (a part-for-the-whole synecdoche).

During the period of Mamluk (1250–1517) and Ottoman rule (1517–1917), the wider compound began to also be popularly known as the Haram al-Sharif, or al-Ḥaram ash-Sharīf (Arabic: اَلْـحَـرَم الـشَّـرِيْـف), which translates as the "Noble Sanctuary". It mirrors the terminology of the Masjid al-Haram in Mecca; This term elevated the compound to the status of Haram, which had previously only been reserved for the Masjid al-Haram in Mecca and the Al-Masjid an-Nabawi in Medina. Other Islamic figures disputed the haram status of the site. Usage of the name Haram al-Sharif by local Palestinians has waned in recent decades, in favor of the traditional name of Al-Aqsa Mosque.

In 637, the Rashidun Caliphate under Umar, the father-in-law of the Islamic prophet Muhammad, besieged and captured Jerusalem from the Byzantine Empire. There are no contemporary records, but many traditions, about the origin of the main Islamic buildings on the Temple Mount. A popular account from later centuries is that Umar was led to the place reluctantly by the Christian patriarch Sophronius. He found it covered with rubbish, but the sacred Rock was found with the help of a converted Jew, Ka'b al-Ahbar. Al-Ahbar advised Umar to build a mosque to the north of the rock, so that worshippers would face both the rock and Mecca, but instead Umar chose to build it to the south of the rock. It became known as al-Aqsa Mosque. According to Muslim sources, Jews participated in the construction of the haram, laying the groundwork for both al-Aqsa and the Dome of the Rock mosques. The first known eyewitness testimony is that of the pilgrim Arculf who visited about 670. According to Arculf's account as recorded by Adomnán, he saw a rectangular wooden house of prayer built over some ruins, large enough to hold 3,000 people.

In 691, an octagonal Islamic building topped by a dome was built by the Caliph Abd al-Malik around the Foundation Stone, for a myriad of political, dynastic and religious reasons, built on local and Quranic traditions articulating the site's holiness, a process in which textual and architectural narratives reinforced one another. The shrine became known as the Dome of the Rock (قبة الصخرة, Qubbat as-Sakhra). (The dome itself was covered in gold in 1920.) In 715 the Umayyads, led by the Caliph al-Walid I, built al-Aqsa Mosque (المسجد الأقصى, al-Masjid al-'Aqṣā, lit. "Furthest Mosque"), corresponding to the Islamic belief of Muhammad's miraculous nocturnal journey as recounted in the Quran and hadith. The term "Noble Sanctuary" or "Haram al-Sharif", as it was called later by the Mamluks and Ottomans, refers to the whole area that surrounds that Rock.