Islam is the second-largest religion in Europe after Christianity. Although the majority of Muslim communities in Europe formed recently, there are centuries-old Muslim societies in the Balkans.
Islam entered southern Europe through the expansion of "Moors" of North Africa in the 8th10th centuries; Muslim political entities existed firmly in what is today Spain, Portugal, Sicily and Malta for several centuries. The Muslim community in these territories was converted or expelled by the end of the 15th century by Christian polities (see Reconquista). Islam expanded into the Caucasus through the Muslim conquest of Persia in the 7th century. The Ottoman Empire expanded into southeastern Europe, invading and conquering huge portions of the Byzantine Empire in the 14th and 15th centuries. Over the centuries, the Ottoman Empire also gradually lost almost all of its European territories, until the empire collapsed in 1922. Some Balkan countries continue to have large populations of native Muslims, though the majority are secular.
The term "Muslim Europe" is used for the Muslim-majority countries of Albania, Kosovo and Bosnia and Herzegovina. Transcontinental countries, such as Turkey, Azerbaijan and Kazakhstan have large Muslim populations, as does Russia in the North Caucasus.
In the late 20th and early 21st centuries, large numbers of Muslims immigrated to Western Europe. By 2010, an estimated 44 million Muslims were living in Europe (6%), including an estimated 19 million in the EU (3.8%). They are projected to comprise 8% by 2030. They are often the subject of intense discussion and political controversy created by events such as terrorist attacks, the cartoons affair in Denmark, debates over Islamic dress, and ongoing support for populist right-wing parties that view Muslims as a threat to European culture. Such events have also fueled growing debate regarding the topic of Islamophobia, attitudes toward Muslims and the populist right.