Fez (/fɛz/) or Fes (/fɛs/; Arabic: فاس, romanized: fās) is a city in northern inland Morocco and the capital of the Fez-Meknes administrative region. It is one of the largest cities in Morocco, with a population of 1.256 million, according to the 2024 census. Located to the northwest of the Atlas Mountains, it is surrounded by hills and the old city is centered around the Fez River (Oued Fes) flowing from west to east. Fez has been called the "Mecca of the West" and the "Athens of Africa". It is also considered the spiritual and cultural capital of Morocco.

Founded under Idrisid rule during the 8th century CE, Fez initially consisted of two autonomous and competing settlements. Successive waves of mainly Arab immigrants from Ifriqiya (Tunisia) and al-Andalus (Spain/Portugal) in the early 9th century gave the nascent city its Arab character. After the downfall of the Idrisid dynasty, other empires came and went until the 11th century when the Almoravid Sultan Yusuf ibn Tashfin united the two settlements into what is today's Fes el-Bali (lit. 'Old Fes') quarter, a.k.a. Medina of Fez. Under Almoravid rule, the city gained a reputation for religious scholarship and mercantile activity.

Fez reached its zenith in the Marinid era (13th–15th centuries), regaining its status as political capital. Numerous new madrasas and mosques were constructed, many of which survive today, while other structures were restored. These buildings are counted among the hallmarks of Moorish and Moroccan architectural styles. In 1276 the Marinid sultan Abu Yusuf Yaqub also founded the royal administrative district of Fes Jdid (lit. 'New Fez'), where the Royal Palace (Dar al-Makhzen) is still located today, to which extensive gardens were later added. During this period the Jewish population of the city grew and the Mellah (Jewish quarter) was formed on the south side of this new district. After the overthrow of the Marinid dynasty, the growth of Fez stalled and the city subsequently competed with Marrakesh for political and cultural influence. It became the capital again under the 'Alawi dynasty up until 1912.

The city consists of two old medina quarters, Fes el-Bali and Fes Jdid, and the much larger modern urban Ville Nouvelle area founded during the French colonial era. The Medina of Fez is listed as a World Heritage Site and is one of the world's largest and oldest urban pedestrian zones (car-free areas). It contains the University of al-Qarawiyyin which was founded in 857 and is the oldest continuously functioning institute of higher education in the world. It also contains the Chouara Tannery from the 11th century, one of the oldest tanneries in the world.

The name of the city in Arabic is فاس Fās (or ڢاس in traditional Maghrebi script), from which the English names Fez, Fès, and Fas are derived. According to some traditions, the city's name comes from the Arabic word فأس Faʾs, meaning pickaxe. Various legends have been reported to explain this etymology. One tells the story of a gold pickaxe found on site during the city's construction, while another claims that Idris I used a silver and gold pickaxe to dig alongside his workers. Another account reported by Ibn Abi Zar claims that an ancient city named "Sef" had previously existed on the site and that Idris I reversed the letters of this name to create the name "Fes". It was also suggested that the name is a Znati form of "afas" meaning "ruins", as Fez may have been built on the ruins of an older city. A further hypothesis suggests that it comes from "Fazaz", which is the name of a nearby region, or from "فحص (faẖs)" meaning "plain wide land".

During the rule of the Idrisid dynasty (788 to 974), Fez consisted of two cities: Fās, founded by Idris I, and al-ʿĀliyá, founded by his son, Idris II. During this period the capital city was known as al-ʿĀliyá, with the name Fās being reserved for the separate site on the other side of the river. No Idrisid coins have been found with the name Fez, only al-ʿĀliyá and al-ʿĀliyá Madinat Idris. It is not known whether the name al-ʿĀliyá ever referred to both urban areas. The two cities were united in 1070 and the name Fās was used for the combined site.

The city was first founded in 789 as Madinat Fas on the southeast bank of the Jawhar River (now known as the Fez River) by Idris I, founder of the Idrisid dynasty. Idris I was an Hasanid Sharif from Arabia who was forced to flee the Hejaz after a failed revolt against the Abbasid Caliphate, eventually moving to northern Morocco and conquering much of the area. His son, Idris II, built a settlement called al-ʿĀliyá on the opposing river bank in 809 and moved his capital here from Walili (Volubilis). The early population was composed mostly of Berbers, along with hundreds of Arab warriors from Kairouan who made up Idris II's entourage.

Arab immigration to Fez increased afterwards. Andalusi families of mixed Arab and Iberian descent, who were expelled from Córdoba after a rebellion in 817–818 against al-Hakam I, were one major component of the immigrant population. These families mainly settled in Madinat Fas. The immigrants from Kairouan and al-Andalus gave the city its Arabic character and would subsequently give their name to the districts of 'Adwat Al-Andalus  [ar] and 'Adwat al-Qarawiyyin  [ar]. The city also had a prominent Jewish community, probably consisting of Zenata Berbers who had previously converted to Judaism, as well as a small remaining Christian population for a time. The Jews were especially concentrated in a northeastern district of al-ʿĀliyá, known as Funduq el-Yihoudi (near the present-day Bab Guissa gate).