The Idrisid dynasty or Idrisids (Arabic: الأدارسة al-Adārisah) were an Arab Muslim dynasty from 788 to 974, ruling most of present-day Morocco and parts of present-day western Algeria. Named after the founder, Idris I, the Idrisids were an Alid dynasty descended from Muhammad through his grandson Hasan. Their reign played an important role in the early Islamization of Morocco and also presided over an increase in Arab immigration and Arabization in major urban centers.

Fleeing the Abbasid Caliphate to the east in the aftermath of the Battle of Fakhkh, Idris I first established himself in 788 at Volubilis in present-day Morocco with the help of local Berber allies. He and his son, Idris II, subsequently founded what became the city of Fez further east. Fez became the capital of an Idrisid state which ruled most of present-day Morocco and part of western Algeria. After Idris II's death, the realm was divided between his rival sons. After a period of conflict, the dynasty's authority resumed and remained relatively stable between 836 and 863. In the late 9th century, however, they faced repeated challenges and local opposition. In the 10th century the region came under the political domination of Zenata tribes who fought proxy battles on behalf of two rival powers in the region, the Fatimid Caliphate and the Umayyad Caliphate of Córdoba. The Idrisids were definitively expelled from Fez in 927, but held onto to a reduced territory in the north of Morocco from their base at Hajar an-Nasr. They were finally defeated and removed from power in 974, and a brief attempt to regain power in 985 also failed.

By the second half of the 8th century the westernmost regions of the Maghreb, including present-day Morocco, had been effectively independent of the Umayyad Caliphate since the Khariji-led Berber revolts that started in 739–40. The Abbasid Caliphate after 750 had no more success in re-establishing control over Morocco. The overthrow of eastern authority meant that Morocco was controlled by various local Berber tribes and principalities which emerged around this time, such as the Barghwata Confederacy on the Atlantic coast and the Midrarid Emirate in Sijilmasa.

The founder of the Idrisid dynasty was Idris ibn Abdallah (788–791), who traced his ancestry back to Ali ibn Abi Talib (died 661) and his wife Fatimah, daughter of the Islamic prophet, Muhammad. He was the great-grandchild of Hasan ibn Ali. After the Battle of Fakhkh, near Mecca, between the Abbasids and supporters of the descendants of Muhammad, Idris ibn Abdallah fled to the Maghreb. He first arrived in Tangier, the most important city of Morocco at the time, and by 788 he had settled in Volubilis (known as Walili in Arabic).

The powerful Awraba Berbers of Volubilis took in Idris and made him their 'imam' (religious leader). The Awraba tribe had supported Kusayla in his struggle against the Ummayad armies in the 670s and 680s. By the second half of the 8th century they had settled in northern Morocco, where their leader Ishak had his base in the Roman town of Volubilis. By this time the Awraba were already Muslim, but lived in an area where most tribes were either Christian, Jewish, Khariji or pagan. The Awraba seem to have welcomed a Sharifi imam as a way to strengthen their political position. Idris I, who was very active in the political organization of the Awraba, began by asserting his authority and working toward the subjugation of the Christian and Jewish tribes. In 789 he founded a settlement south east of Volubilis, called Medinat Fas. In 791 Idris I was poisoned and killed by an Abbasid agent. Even though he left no male heir, shortly after his death, his wife Lalla Kanza bint Uqba al-Awrabi, bore him his only son and successor, Idris II. Idris' loyal Arab ex-slave and companion Rashid brought up the boy and took on himself the regency of the state, on behalf of the Awraba. In 801 Rashid was killed by the Abbasids. In the following year, at the age of 11 years, Idris II was proclaimed imam by the Awraba.

Even though he had spread his authority across much of northern Morocco, as far west as Tlemcen, Idris I had been completely dependent on the Awraba leadership. Idris II began his rule with the weakening of Awraba power by welcoming Arab settlers in Walili and by appointing two Arabs as his vizier and qadi. Thus he transformed himself from a protégé of the Awraba into their sovereign. The Awraba leader Ishak responded by plotting against his life with the Aghlabids of Tunisia. Idris reacted by having his former protector Ishak killed, and in 809 moved his seat of government from the Awraba dominated Walili to Fes, where he founded a new settlement named Al-'Aliya. Idris II (791–828) developed the city of Fez, established earlier by his father as a Berber market town. Here he welcomed two waves of Arab immigration: one in 818 from Cordoba and another in 824 from Aghlabid Tunisia, giving Fes a more Arab character than other Maghrebi cities. When Idris II died in 828, the Idrisid state spanned from western Algeria to the Sous in southern Morocco and had become the leading state of Morocco, ahead of the principalities of Sijilmasa, Barghawata and Nekor which remained outside their control.

The dynasty's power would slowly decline following Idris II's death. Under his son and successor Muhammad (828–836) the kingdom was divided amongst seven of his brothers, whereby eight Idrisid statelets formed in Morocco and western Algeria. Muhammad himself came to rule Fes, with only nominal power over his brothers. His brother Al-Qasim ruled Tangier and its surroundings. 'Umar ruled over the Sanhaja and the Ghumara in the Rif region. Isa was given control of the coastal Tamesna regions near the Bou Regreg, including Shallah (Chellah), and was based at Wazeqqūr (a town near modern-day Khenifra). Yahya was given Hiṣn Daī (a site probably near modern Beni Mellal). Hamza was given Walili. 'Ubayd Allah (or 'Abd Allah) was given the south, including the territory of the Lamta tribes and a town named Tamdult. Agadir (later Tlemcen) was left under the control of Muhammad Ibn Sulayman, Idris II's cousin and the son of Sulayman, the brother of Idris I whom the latter had left in charge of the city, constituting the Sulaymanid dynasty.

Soon after this territorial division Isa revolted against his brother Muhammad. Muhammad entrusted his other brother Umar to punish him. Umar successfully drove Isa from power, who was forced to take refuge in Chellah. Umar then turned north to punish his other brother, al-Qasim, because the latter had refused to join him and Muhammad against Isa. Al-Qasim fled to Asilah and settled nearby, while Muhammad gave Umar governorship of Tangier as a reward. Upon Umar's death in September or October 835 his son Ali ibn Umar was granted all of his father's domains in turn. Muhammad himself died seven months later in the March or April 836. His son Ali ibn Muhammad inherited his position and ruled for 13 years (836–849) in a competent manner, ensuring the stability of the state. After his death in 849 he was succeeded by his brother Yahya ibn Muhammad (or Yahya I), who also enjoyed a peaceful reign.