Greater Albania (Albanian: Shqipëria e Madhe) is an irredentist and nationalist concept that seeks to annex the lands that many Albanians consider to form their national homeland. It is based on claims on the present-day or historical presence of Albanian populations in those areas. In addition to the existing Albania, the term incorporates claims to regions in the neighbouring states, the areas include Kosovo, the Preševo Valley of Serbia, territories in southern Montenegro, northwestern Greece (the Greek regional units of Thesprotia and Preveza, referred by Albanians as Chameria, and other territories that were part of the Vilayet of Yanina during the Ottoman Empire), and a western part of North Macedonia. The combination of the populations of these countries and territories of other countries sustaining large ethnic Albanian communities enumerate to over 4 million people.

The unification of an even larger area into a single territory under Albanian authority had been theoretically conceived by the League of Prizren, an organization of the 19th century whose goal was to unify the Albanian inhabited lands (and other regions, mostly from the regions of Macedonia and Epirus) into a single autonomous Albanian Vilayet within the Ottoman Empire, which was briefly achieved de jure in September 1912. The concept of a Greater Albania, as in greater than Albania within its 1913 borders, was conceived and implemented under the fascist Italian and Nazi German occupation of the Balkans during World War II. The idea of unification has roots in the events of the Treaty of London in 1913, when roughly 50% of the predominantly Albanian territories and 40% of the population were left outside the new country's borders.

Albanian nationalists dislike the expression "Greater Albania" and prefer to use the term "Ethnic Albania". Ethnic Albania (Albanian: Shqipëria Etnike) is a term used primarily by Albanian nationalists to denote the territories claimed as the traditional homeland of ethnic Albanians, despite these lands also being inhabited by many non-Albanians. Those that use the second term refer to an area which is smaller than the four Ottoman vilayets, while still encompassing Albania, Kosovo, western North Macedonia, Albanian populated areas of Southern Serbia and parts of Northern Greece (Chameria) that had a historic native Albanian population. Albanian nationalists ignore that within these regions there are also sizable numbers of non-Albanians. Another term used by Albanians, is "Albanian national reunification" (Albanian: Ribashkimi kombëtar shqiptar).

Prior to the Balkan wars of the beginning of the 20th century, Albanians were subjects of the Ottoman Empire. The Albanian independence movement emerged in 1878 with the League of Prizren (a council based in Kosovo) whose goal was cultural and political autonomy for ethnic Albanians inside the framework of the Ottoman Empire. However, the Ottomans were not prepared to grant The League's demands. Ottoman opposition to the League's cultural goals eventually helped transform it into an Albanian national movement.

Albanian nationalism overall was a reaction to the gradual breakup of the Ottoman Empire and a response to Balkan and Christian national movements that posed a threat to an Albanian population that was mainly Muslim. Efforts were devoted to including vilayets with an Albanian population into a larger unitary Albanian autonomous province within the Ottoman state while Greater Albania was not considered a priority. Albanian nationalism during the late Ottoman era was not imbued with separatism that aimed to create an Albanian nation-state, though Albanian nationalists did envisage an independent Greater Albania. Albanian nationalists were mainly focused on defending rights that were sociocultural, historic and linguistic within existing countries without being connected to a particular polity.

The imminence of collapsing Ottoman rule through military defeat during the Balkan wars pushed Albanians represented by Ismail Qemali to declare independence (28 November 1912) in Vlorë from the Ottoman Empire. The main motivation for independence was to prevent Balkan Albanian inhabited lands from being annexed by Greece and Serbia. Italy and Austria-Hungary supported Albanian independence due to their concerns that Serbia with an Albanian coast would be a rival power in the Adriatic Sea and open to influence from its ally Russia. Apart from geopolitical interests, some Great powers were reluctant to include more Ottoman Balkan Albanian inhabited lands into Albania due to concerns that it would be the only Muslim dominated state in Europe. Russo-French proposals were for a truncated Albania based on central Albania with a mainly Muslim population, which was also supported by Serbia and Greece who considered that only Muslims could only be Albanians. As more Albanians became part of the Serbian and Greek states, Albanian scholars with nationalistic perspectives interpret the declaration of independence as a partial victory for the Albanian nationalist movement.

On 7 April 1939, Italy's Benito Mussolini, after a prolonged interest and overarching sphere of influence during the interwar period, invaded Albania. Italian fascists like Count Galeazzo Ciano pursued Albanian irredentism, believing it would earn Italy support among Albanians while aligning with Italy's war aim of Balkan conquest. The Italian annexation of Kosovo to Albania was popular with Albanians in both areas. The Western part of North Macedonia was also annexed to the Italian protectorate of Albania. In these territories, all (including non-Albanians) were obliged to attend Albanian schools that taught a nationalistic and fascist curriculum; all were compelled to use or adopt Albanian names and surnames. Elites, such as landowners and liberal nationalists opposed to communism, formed the Balli Kombëtar organisation; they and the collaborationist government sought to preserve Greater Albania.

Many Kosovo Albanians were preoccupied with driving out the Serb community, particularly the post-1919 Serb and Montenegrin colonists, often settled on confiscated Albanian property. Albanians saw Serbian and Yugoslav rule as foreign, and according to Ramet they felt that anything would be better than the chauvinism, corruption, administrative hegemonism and exploitation they had experienced under the Serbian authorities. Albanians collaborated broadly with the Axis occupiers, who had promised them a Greater Albania. Collapse of Yugoslav rule resulted in actions of revenge being undertaken by Albanians, some joining the local Vulnetari militia that burned Serb settlements and killed Serbs while interwar Serb and Montenegrin colonists were expelled into Territory of the Military Commander in Serbia. The aim of these actions was to create a homogeneous Greater Albanian state. Italian authorities in Kosovo allowed the use of the Albanian language in schools, university education, and administration. The same nationalist, Albanian elements who welcomed Kosovo's Albanians into an enlarged state also worked against the Italians, viewing them as foreign occupiers. An attempt to get Kosovan Albanians to join the resistance, a meeting in Bujan (1943–1944), northern Albania was convened between Balli Kombëtar members and Albanian communists that agreed to common cause and maintain the expanded boundaries. The deal was opposed by Yugoslav partisans, and later rescinded, resulting in limited enthusiasm among Kosovan Albanian recruits. Some Balli Kombëtar members such as Shaban Polluzha became partisans with the view that Kosovo would become part of Albania. At the war's end, some Kosovar Albanians felt betrayed by the return to Yugoslav rule, and for several years, Albanian nationalists in Kosovo resisted both the Partizans and later the new Yugoslav army. Albanian nationalists viewed their inclusion within Yugoslavia as an occupation.