The term Greater Serbia or Great Serbia describes the Serbian nationalist and irredentist ideology of the creation of a Serb state which would incorporate all regions of traditional significance to Serbs, a South Slavic ethnic group, including regions outside modern-day Serbia that are partly populated by Serbs. The initial movement's main ideology (Pan-Serbism) was to unite all Serbs into one state, claiming, depending on the version, different areas of many surrounding countries, regardless of non-Serb populations present.

Serbian nationalism asserts that Serbs are a nation and promotes the cultural and political unity of Serbs. It is an ethnic nationalism, originally arising in the context of the general rise of nationalism in the Balkans under Ottoman rule, under the influence of Serbian linguist Vuk Stefanović Karadžić and Serbian statesman Ilija Garašanin. Serbian nationalism was an important factor during the Balkan Wars which contributed to the decline of the Ottoman Empire, during and after World War I when it contributed to the dissolution of the Austro-Hungarian Empire, and again during the breakup of Yugoslavia and the Yugoslav Wars of the 1990s.