Islam in Afghanistan began to be practiced after the Arab Islamic conquest of Afghanistan from the 7th to the 10th centuries, with the last holdouts to conversion submitting in the late 19th century. It was generally accepted by local communities as a replacement of Zoroastrianism and Buddhism, local tribes began converting to the new religion. Islam is the official state religion of Afghanistan, with approximately 99.7% of the Afghan population being Muslim. Roughly 90% practice Sunni Islam, while around 10% are Shias.^[4][5] Most Shias belong to the Twelver branch and only a smaller number follow Ismailism.^[4]

After the Islamic conquest of Persia was completed, the Muslim Arabs then began to move towards the lands east of Persia and in 652 captured Herat.^[6] By the end of the 10th century CE the Turkic Ghaznavids subdued Kabul Shahi kings.

During the 7th century, the Rashidun Caliphate Arabs entered the territory that is now Afghanistan after defeating the Sassanian Persians in Nihawand. After this colossal defeat, the last Sassanid emperor, Yazdegerd III, fled eastward deep into Central Asia. In pursuing Yazdegerd, the Arabs entered the area from northeastern Iran^[7] via Herat, where they stationed a large portion of their army before advancing toward northern Afghanistan.

Many of the inhabitants of northern Afghanistan accepted Islam through Umayyad missionary efforts, particularly under the reign of Caliph Hisham and Umar ibn AbdulAziz.^[8] In the south, Abdur Rahman bin Samara made incursions into Zabulistan which was ruled by the Zunbils.^[9]

During the reign of Al-Mu'tasim and his successors, Islam was generally practiced by most inhabitants of the region, and after Abbasid decline, under Ya'qub-i Laith Saffari, Islam was the predominant religion of Kabul and other major cities of Afghanistan. The father of Abu Hanifa, Thabit bin Zuta, was born in the territory that is now Afghanistan. He emigrated to Kufa (in Iraq), where Hanifa was born. Later, the Samanids propagated Sunni Islam deep into Central Asia, and the first complete translation of the Qur'an into Persian was made in the 9th century. Since then, Islam has dominated the country's religious landscape. Islamic leaders have entered the political sphere at various times of crisis but rarely exercised secular authority for long.

The remnants of a Shahi presence in Peshawar were expelled by Mahmud of Ghazni in 998 and 1030.^[10] The Ghaznavids were replaced by the Ghurid dynasty who expanded the already powerful Islamic empire. The Friday Mosque of Herat is one of the oldest mosques in the country, believed to have been first built under the Ghurids in the 12th century. During this period, known as the Islamic Golden Age, Afghanistan became the second major center of learning in the Muslim world after Baghdad.^[11][12]

After the Mongol invasion and destruction, the Timurids rebuilt the area and once again made it a center of Islamic learning. Shia Islam made its way to southern Afghanistan during the Safavid rule in the 16th century. Until Mir Wais Hotak liberated the Afghans in 1709, the Kandahar region of Afghanistan was often a battleground between the Shia Safavids and the Sunni Mughals.

For Afghans, Islam represents a potentially unifying symbolic system which offsets the divisiveness that frequently rises from the existence of a deep pride in tribal loyalties and an abounding sense of personal and family honor found in multitribal and multiethnic societies such as Afghanistan.

Islam is a central, pervasive influence throughout Afghan society; religious observances punctuate the rhythm of each day and season. In addition to a central congregational Mosque for weekly communal prayers which are obligatory for men in Islam (but not for woman) and are generally well attended, smaller community-maintained mosques stand at the center of villages, as well as town and city neighborhoods. Masjids serve not only as places of worship, but for a multitude of functions, including shelter for guests, places to meet, the focus of social religious festivities and schools. Almost every Afghan has at one time during his youth studied at a mosque school; for many this is the only formal education they receive.^{[citation needed]}

Because Islam is a totalitarian way of life and functions as a comprehensive code of social behavior regulating all human relationships, individual and family status depends on the proper observance of the society's value system based on concepts defined in Islam. These are characterized by honesty, frugality, generosity, virtuousness, piousness, fairness, truthfulness, tolerance and respect for others. To uphold family honor, elders also control the behavior of their children according to these same Islamic prescriptions. At times, even competitive relations between tribal or ethnic groups are expressed in terms claiming religious superiority. In short, Islam structures day-to-day interactions of all members of the community.

The religious establishment has several levels. Any Muslim can lead informal groups in prayer. Mullahs who officiate at mosques are normally appointed by the government after consultation with their communities and, although partially financed by the government, mullahs are largely dependent for their livelihood on community contributions including shelter and a portion of the harvest. Supposedly versed in the Qur'an, Sunnah, Hadith and Shariah, they must ensure that their communities are knowledgeable in the fundamentals of Islamic ritual and behavior. This qualifies them to arbitrate disputes over religious interpretation. Often they function as paid teachers responsible for religious education classes held in mosques where children learn basic moral values and correct ritual practices. Their role has additional social aspects for they officiate on the occasion of life crisis rituals associated with births, marriages and deaths.

But rural mullahs are not part of an institutionalized hierarchy of clergy. Most are part-time mullahs working also as farmers or craftsmen. Some are barely literate, or only slightly more educated than the people they serve. Often, but by no means always, they are men of minimal wealth and, because they depend for their livelihood on the community that appoints them, they have little authority even within their own social boundaries. They are often treated with scant respect and are the butt of a vast body of jokes making fun of their arrogance and ignorance. Yet their role as religious arbiters forces them to take positions on issues that have political ramifications and since mullahs often disagree with one another, pitting one community against the other, they are frequently perceived as disruptive elements within their communities.

Veneration of saints and shrines is opposed by some Islamic groups, particularly those ascribing to the Salafi or Ahle Hadith. Nevertheless, Afghanistan's landscape is liberally strewn with shrines honoring saints of all descriptions. Many of Afghanistan's oldest villages and towns grew up around shrines of considerable antiquity. Some are used as sanctuaries by fugitives.

Shrines vary in form from simple mounds of earth or stones marked by pennants to lavishly ornamented complexes surrounding a central domed tomb. These large establishments are controlled by prominent religious and secular leaders. Shrines may mark the final resting place of a fallen hero (shahid), a venerated religious teacher, a renowned Sufi poet, or relics, such as a hair of Muhammad or a piece of his cloak (khirqah). A great many commemorate legends about the miraculous exploits of Ali ibn Abi Talib, the fourth caliph and the first Imam of Shi'a Islam believed to be buried at the nation's most elaborate shrine located in the heart of Mazari Sharif, the Exalted Shrine. Ali is revered throughout Afghanistan for his role as an intermediary in the face of tyranny.

Festive annual fairs celebrated at shrines attract thousands of pilgrims and bring together all sections of communities. Pilgrims also visit shrines to seek the intercession of the saint for special favors, be it a cure for illness or the birth of a son. Women are particularly devoted to activities associated with shrines. These visits may be short or last several days and many pilgrims carry away specially blessed curative and protective amulets (usually a tawiz) to ward off the evil eye, assure loving relationships between husbands and wives and many other forms of solace. Like saint veneration, such practices are generally not encouraged in Islam according to classical understanding of the Holy Qu'ran and Hadiths (prophetic sayings of the Rabi)

Roughly 10% of the Afghan population is Shia.^[4][5] Majority of Shias in Afghanistan belong to the Twelver branch. This includes the Hazara ethnic group and the smaller urbanized Qizilbash group, who are originally from eastern Iran.

Politically aware Shia students formed the Afghan Maoist movement in the 1960s and early 1970s. After the Saur Revolution (April Revolution) of 1978 and the Iranian Revolution of 1979, Shia rebel groups in the Hazarajat region, although frequently at odds with one another, became active in mujahideen activities. They were aided by Shi'a Iran and fought against the Soviet-backed Afghan government as well as other mujahideen groups.

During the political maneuvering leading up to the establishment of the Islamic State of Afghanistan in 1992, the Shi'a groups unsuccessfully negotiated for more equitable, consequential political and social roles.

Three Sufi orders are prominent: the Naqshbandiya founded in Bukhara, the Qadiriya founded in Baghdad, and the Cheshtiya located at Chesht-i-Sharif east of Herat. Among the Naqshbandi, Ahmad al Faruqi Kabuli, born north of Kabul, acquired renown for his teachings in India during the reign of the Moghul Emperor Akbar in the sixteenth century.

Another famous Qadiriya pir named Mawlana Faizani came to prominence in the 1960s and 1970s, and was a leading critic against the creeping influence of communist philosophy. Jailed in the mid-70s, Mawlana Faizani disappeared when the khalqis came to power and remains missing to this day.

The Cheshtiya order was founded by Mawdid al-Cheshti who was born in the twelfth century and later taught in India. The Cheshtiya brotherhood, concentrated in the Hari River valley around Obe, Karukh and Chehst-i-Sharif, is very strong locally and maintains madrasas with fine libraries. Traditionally the Cheshtiya have kept aloof from politics, although they were effectively active during the resistance within their own organizations and in their own areas.

Herat and its environs has the largest number and greatest diversity of Sufi branches, many of which are connected with local tombs of pir (ziarat). Other Sufi groups are found all across the north, with important centers in Maimana, Faryab Province, and in Kunduz. The brotherhoods in Kabul and around Mazari Sharif are mostly associated with the Naqshbandiya. The Qadiriya are found mainly among the eastern Pashtun of Wardak, Paktia and Nangarhar, including many Ghilzai nomadic groups. Other smaller groups are settled in Kandahar and in Shindand, Farah Province. The Cheshtiya are centered in the Hari River valley. There are no formal Sufi orders among the Shi'a in the central Hazarajat, although some of the concepts are associated with Sayyids, descendants of Mohammad, who are especially venerated among the Shi'a.

Afghanistan is unique in that there is little hostility between the ulama (religion scholars) and the Sufi orders. A number of Sufi leaders are considered as ulama, and many ulama closely associate with Sufi brotherhoods. The general populace accords Sufis respect for their learning and for possessing karamat, the psychic spiritual power conferred upon them by God that enables pirs to perform acts of generosity and bestow blessings (barakat). Sufism therefore is an effective popular force. In addition, since Sufi leaders distance themselves from the mundane, they are at times turned to as more disinterested mediators in tribal disputes in preference to mullahs who are reputed to escalate minor secular issues into volatile confrontations couched in Islamic rhetoric.

Despite the Afghan Sufis' stable position in Afghan society, Sufi leaders were among those executed following the Saur Revolution, among them Baha'uddin Jan, the pir naqshbandi of the Aimaq of Purchaman District, Farah.^[22]

• Islam by country
• Islam in South Asia
• Education in Afghanistan
• List of mosques in Afghanistan
• Religion in Afghanistan
• Women in Islam