Islam is the largest and the state religion of the People's Republic of Bangladesh. According to the 2022 census, Bangladesh had a population of about 150 million Muslims, or 91.04% of its total population of million.

Islam arrived in modern-day Bangladesh in the late 7th century, when Arab Muslims established commercial as well as religious connection in the region of Bengal, mainly through the coastal regions as traders and primarily via the ports of Chittagong. In the early 13th century, Muhammad bin Bakhtiyar Khalji conquered Western and part of Northern Bengal, establishing the first Muslim kingdom in Bengal. During the 13th century, Sufi missionaries, mystics and saints began to preach Islam in villages.

The Bengal region emerged as a supreme power of the medieval Islamic East. The Bengal Sultanate united Bengal on an ethno-linguistic platform, and the region reached in her golden age. Later on, Mughal Bengal became increasingly independent under the Nawabs in the 18th century. Muslim nationalism rose during British rule which ultimately led to the establishment of East Pakistan in 1947. Following the 1971 Liberation War, East Pakistan seceded from Pakistan and modern Bangladesh was established. Founded as a constitutionally secular state, Islam was declared as the state religion of Bangladesh in 1988. However, Bangladesh remains a de facto secular country.

Muslims of Bangladesh are predominant native Bengali Muslims. The majority of Bangladeshis are Sunni, and follow the Hanafi school of thought and fiqh. Minority denominations include Shi'ism and Ahmadiyya. Bangladesh also has a firmly rooted Sufi tradition, which played pivotal role in the Islamic conversion of the country. Islam constitutes a major component of the Culture of Bangladesh, influencing education, architecture, clothing, sculpture, theatre, music and festivals. Bangladeshi Muslims have retained and integrated many indigenous elements and cultural practices upon the spread of Islam.

Islamic affairs in the country (such as Hajj and Zakat) are regulated by the Ministry of Religious Affairs and Islamic Foundation Bangladesh. Sharia is only leagally applied in personal affairs (such as marriage and inheritance) through British era legal codes.

History Early explorers

One of the earliest mosques in South Asia is under excavation in northern Bangladesh, indicating the presence of Muslims in the area around the lifetime of Muhammad. By the 9th century, Muslim merchants had increased trade with Bengali seaports, introducing Islam to the region. Coins from the Abbasid era have been discovered across Bengal, further evidencing this connection. Additional evidence of these early Arab traders includes inscriptions found near the Meghna River close to Sandwip on the Bay of Bengal. Arab writers of the time also mentioned the kingdoms of Samrup and Rumi, the latter being identified with the empire of Dharmapala of the Pala Empire.

In the 10th century, Samatata, located in southeastern Bengal, was home to a diverse population with various religious backgrounds. During this period, the Arab geographer Al-Masudi visited the region and documented a thriving Muslim community in his work The Meadows of Gold. Islam first appeared in Bengal during Pala dynasty's rule, as a result of increased trade between Bengal and the Arab Abbasid Caliphate, facilitating the presence of Arab traders along the coast of Bengal which includes Port of Chittagong.

In addition to trade, Islam was also being introduced to the people of Bengal through the migration of Sufi missionaries prior to conquests. The earliest known Sufi missionaries were Syed Shah Surkhul Antia and his students, most notably Shah Sultan Rumi, in the 11th century. Rumi settled in present-day Netrokona, Mymensingh where he influenced the local ruler and population to embrace Islam.

The first Muslim conquest of Bengal was undertaken by the forces of General Bakhtiyar Khilji in the thirteenth century. This opened the doors for Muslim influence in the region for hundreds of years up until the present-day. Many of the people of Bengal began accepting Islam through the influx of missionaries following this conquest. Sultan Balkhi and Shah Makhdum Rupos settled in the present-day Rajshahi Division in northern Bengal, preaching to the communities there. Numerous small sultanates emerged in the region. During the reign of the Sultan of Lakhnauti Shamsuddin Firuz Shah, much of present-day Satgaon, Sonargaon and Mymensingh came under Muslim dominion. A community of 13 Muslim families headed by Burhanuddin resided in the northeastern city of Srihatta (Sylhet), claiming their descendants to have arrived from Chittagong. Srihatta (Sylhet) was ruled by an oppressive king called Gour Govinda. After being informed of Raja Gour Govinda's oppressive regime in Sylhet, Firuz Shah sent numerous forces led by his nephew Sikandar Khan Ghazi and subsequently his military commander-in-chief Syed Nasiruddin to conquer Sylhet. By 1303, over three hundred Sufi preachers led by Shah Jalal aided the conquest and confirmed a victory. Following the conquest, Jalal disseminated his followers across different parts of Bengal to spread Islam. Jalal is now a household name among Muslims in Bangladesh.

Sultanate of Bengal

The establishment of a single united Bengal Sultanate in 1352 by Shamsuddin Ilyas Shah finally gave rise to a "Bengali" socio-linguistic and cultural identity. The Ilyas Shahi dynasty highly acknowledged Muslim scholarship. Usman Serajuddin, also known as Akhi Siraj Bengali, was a native of Gaur in western Bengal and became the Sultanate's court scholar during Ilyas Shah's reign. The sovereign Sunni Muslim nation-state also enabled the language of the Bengali people to gain patronage and support, contrary to previous states which exclusively favoured Sanskrit, Pali and Persian. The converted Sultan Jalaluddin Muhammad Shah funded the construction of Islamic seminaries as far as Mecca and Madina in the Middle East. The people of Arabia came to know these institutions as al-Madaris al-Bangaliyyah (Bengali madrasas).

Moroccan traveler Ibn Battuta's diary is one of the best known accounts of the prelude to the Bengal Sultanate. Ibn Battuta visited Bengal during the reign of Sultan Fakhruddin Mubarak Shah, a rebel governor of the Delhi Sultanate who established a city state in Sonargaon. At the time, Bengal was divided into the three city states of Sonargaon, Satgaon and Lakhnauti. In 1352, the three city states were united by Ilyas Shah into a single, unitary, independent Bengal Sultanate. The creation of the Bengal Sultanate sparked several Bengal-Delhi Wars, which resulted in Delhi recognizing Bengal's independence. The Ilyas Shahi dynasty consolidated Bengali statehood, the economy and diplomatic relations. A network of Mint Towns – provincial capitals which produced the Sultan's sovereign currency called the taka – was established across Bengal. The Bengali state followed the Persian model of statecraft. Muslims from other parts of the world were imported for military, bureaucratic and household services. These immigrants included Turks from northern India who were originally recruited in Central Asia; as well as Abyssinians imported via East Africa into the Bengali port of Chittagong. A highly commercialized and monetized economy evolved. Islamic architecture was introduced on a major scale. A huge mosque called the Adina Mosque was built following the design of the Great Mosque of Damascus. A distinct Bengali Muslim architectural style developed, with terracotta and stone buildings showing a fusion of Persian and Bengali elements. Mosques included two categories, including multi-domed rectangular structures and single-domed square structures. A distinct style of Bengali mihrabs, minbars, terracotta arabesque, and do-chala roofs developed; this influence also spread to other regions.

The Bengal Sultanate was ruled by five dynastic periods, with each period have a particular ethnic identity. The Ilyas Shahi dynasty was of Turkic origin. It was replaced by the Bengali-origin dynasty of Jalaluddin Muhammad Shah and Shamsuddin Ahmad Shah for a few decades before being restored. In the 1490s, a series of Abyssinian generals took turns in becoming the Sultan of Bengal. They were succeeded by the Hussain Shahi dynasty which was of Arab origin. They were in turn replaced by the Pashtun rulers of the Suri dynasty, who first acted as regional governors before restoring Bengali independence. The last dynasty, the Karrani dynasty, was also of Pashtun origin. The sultanate period saw a flourishing of Islamic scholarship and the development of Bengali literature. Scholars, writers and poets of sultanate-era Bengal included Usman Serajuddin, Alaul Haq, Sheikh Nur Qutb Alam, Alaol, Shah Muhammad Sagir, Abdul Hakim, Syed Sultan, Qadi Ruknu'd-Din Abu Hamid Muhammad bin Muhammad al-'Amidi, Abu Tawwama, Syed Ibrahim Danishmand, Syed Arif Billah Muhammad Kamel and Syed Muhammad Yusuf among others. Bengal's tradition of Persian prose was acknowledged by Hafez. The Dobhashi tradition saw Bengali transliteration of Arabic and Persian words in Bengali script to illustrate Islamic epics and stories.

During the independent sultanate period, Bengal forged strong diplomatic relations with empires outside the subcontinent. The most notable of these relationships was with Ming China and its emperor Yongle. At least a dozen embassies were exchanged between China and Bengal. The Sultan of Bengal even gifted an East African giraffe to the Emperor of China as a tribute to China-Bengal relations. The Chinese Muslim admiral Zheng He visited Bengal as an envoy of the Emperor of China. Bengali ships transported the embassies of Sumatra, Brunei and Malacca to the port of Canton. China and the Timurid ruler of Herat mediated an end to the Bengal Sultanate-Jaunpur Sultanate War. The Sultan of Bengal also acknowledged the nominal authority of the Abbasid caliph in Cairo. The Portuguese was the first European state entity to establish relations with the Bengal Sultanate. The Bengal Sultan permitted the opening of the Portuguese settlement in Chittagong.

During the Sultanate period, a syncretic belief system arose due to mass conversions. As a result, the Islamic concept of tawhid (the oneness of God) was diluted into the veneration of saints or pirs. Deities such as Shitala (goddess of smallpox), Olabibi (goddess of cholera) and Manasa (goddess of snakes) became venerated as pirs.

Under Mughal Empire

In pre-Mughal times, there is less evidence for widespread adoption of Islam in what is now Bangladesh. What mention of Muslims there was usually in reference to an urban elite. Ibn Battuta met with Shah Jalal in Sylhet and noted the inhabitants of the plains were still Hindu. In 1591, Venetian traveller Cesare Federici mentioned Sondwip near Chittagong as having an entirely Muslim population. The seventeenth century European travellers generally understood Islam as being implanted after the Mughal conquest.

During the Mughal Empire, much of the region of what is now East Bengal was still heavily forested, but highly fertile. The Mughals incentivised the bringing of this land under cultivation, and so peasants were incentivised to bring the land under cultivation. These peasants were primarily led by Muslim leaders and so Islam became the main religion in the delta. Most of the Zamindars in the modern Barisal division, for instance, were upper caste Hindus who subcontracted actual jungle clearance work to a Muslim pir. In other instances, pirs themselves would organise the locals to clear the jungle and then contact the Mughals to gain legitimacy. In other instances, such as the densely forested interior of Chittagong, Muslims came from indigenous tribals who never followed Hindu rituals.

In British India