Islam is the second-largest religion in Europe after Christianity. Although the majority of Muslim communities in Western Europe formed as a result of immigration, there are centuries-old indigenous European Muslim communities in the Balkans, Caucasus, Crimea, and Volga region. The term "Muslim Europe" is used to refer to the Muslim-majority countries in the Balkans and the Caucasus (Albania, Azerbaijan, Bosnia and Herzegovina, Kosovo, and Turkey) and parts of countries in Central and Eastern Europe with sizable Muslim minorities (Bulgaria, Montenegro, North Macedonia, and some republics of Russia) that constitute large populations of indigenous European Muslims, although the majority are secular.

Islam expanded into the Caucasus through the Muslim conquest of Persia in the 7th century and entered Southern Europe after the Umayyad conquest of Hispania in the 8th–10th centuries; Muslim political entities existed firmly in what is today Spain, Portugal, Sicily, and Malta during the Middle Ages. The Muslim populations in these territories were either converted to Christianity or expelled by the end of the 15th century by the indigenous Christian rulers (see Reconquista). The Ottoman Empire expanded into Southeastern Europe and consolidated its political power by invading and conquering huge portions of the Serbian and Bulgarian empires, and the remaining territories of the region, including the Albanian and Romanian principalities, and the kingdoms of Bosnia, Croatia, and Hungary between the 14th and 16th centuries. Over the centuries, the Ottoman Empire gradually lost its European territories. Islam was particularly influential in the territories of Albania, Bosnia and Herzegovina, and Kosovo, and has remained the dominant religion in these countries.

During the Middle Ages, Islam spread in parts of Central and Eastern Europe through the Islamization of several Turkic ethnic groups, such as the Cumans, Kipchaks, Tatars, and Volga Bulgars under the Mongol invasions and conquests in Eurasia, and later under the Golden Horde and its successor khanates, with its various Muslim populations collectively referred to as "Turks" or "Tatars". These groups had a strong presence in present-day European Russia, Hungary, and Ukraine during the High Medieval Period.

Historically significant Muslim populations in Europe include Ashkali, Bosniaks, Böszörmény, Balkan Turks, Chechens, Cretan Turks, Crimean Tatars, Gajals, Gorani, Greek Muslims, Ingush, Khalyzians, Lipka Tatars, Muslim Albanians, Muslim Romani people, Pomaks, Torbeshi, Turkish Cypriots, Vallahades, Volga Bulgars, Volga Tatars, Yörüks, and Megleno-Romanians from Notia today living in East Thrace.

The Muslim population in Europe is extremely diverse with varied histories and origins. Today, the Muslim-majority regions of Europe include several countries in the Balkans (Albania, Bosnia and Herzegovina, Kosovo, and the European part of Turkey), some Russian republics in the North Caucasus and the Idel-Ural region, and the European part of Kazakhstan. These communities consist predominantly of indigenous Europeans of the Muslim faith, whose religious tradition dates back several hundred years to the Middle Ages. The transcontinental countries of Turkey, Azerbaijan, and Kazakhstan are also majority Muslim.

In medieval Albania, the rebellion against the Ottomans had already been smouldering for years before Skanderbeg deserted the Ottoman army. The most notable earlier revolt was revolt of 1432–36 led principally by Gjergj Arianiti. Although Skanderbeg was summoned by his relatives during this rebellion, he remained loyal to the sultan and did not fight the Ottomans. After this rebellion was suppressed by the Ottomans, Arianiti again revolted against the Ottomans in the region of central Albania in August 1443.

Skanderbeg decided to leave his position of Ottoman sanjakbey and revolt against the Ottomans only after the victorious Crusade of Varna in 1443. Successes of the crusaders inspired revolt of Skanderbeg and revolt of Constantine XI Palaiologos in the Despotate of the Morea. In early November 1443, Skanderbeg deserted the forces of Sultan Murad II during the Battle of Nish, while fighting against the crusaders of John Hunyadi. Skanderbeg quit the field along with 300 other Albanians serving in the Ottoman army. He immediately led his men to Krujë, where he arrived on November 28, and by the use of a forged letter from Sultan Murad to the Governor of Krujë he became lord of the city. To reinforce his intention of gaining control of the former domains of Zeta, Skanderbeg proclaimed himself the heir of the Balsha family. After capturing some less important surrounding castles (Petrela, Prezë, Guri i Bardhë, Svetigrad, Modrič and others) and eventually gaining control over more than his father Gjon Kastrioti's domains, Skanderbeg abjured Islam and proclaimed himself the avenger of his family and country. He raised a red flag with a black double-headed eagle on it: Albania uses a similar flag as its national symbol to this day.

Until September 1912, the Ottoman government intentionally kept Albanians divided within four ethnically heterogeneous vilayets in order to prevent the national unification of Albania. The reforms introduced by the Young Turks provoked the Albanian Revolt, which lasted from January to August 1912. In January 1912, Hasan Prishtina, an Albanian deputy in the Ottoman parliament, publicly warned members of the parliament that the policy of the Young Turks' government would lead to a revolution in Albania. The Albanian revolt was successful and until August 1912 rebels managed to gain control over whole Kosovo vilayet (including Novi Pazar, Sjenica, Pristina and even Skopje), a part of the Scutari Vilayet (including Elbasan, Përmet and Leskovik), Konitsa in Janina Vilayet and Debar in Monastir Vilayet. The Ottoman government ended the Albanian revolt on 4 September 1912 by accepting all demands related to establishing an unified autonomous system of administration and justice for Albanians within one vilayet—the Albanian vilayet.