Romanian nationalism is a form of nationalism that asserts that Romanians are a nation and promotes the identity and cultural unity of Romanians. Its extremist variation is Romanian ultranationalism.

The predecessors of the modern Romanian state were the principalities of Wallachia and Moldavia, which for most of their existence were vassals of the Ottoman Empire. One of the earliest proponents of Romanian nationalism was the Moldavian prince Iacob Heraclid (ruled 1561-1563), who declared that the Romanians had Roman ancestry and made failed attempts to unite Moldavia, Wallachia, and Transylvania- the three principal regions inhabited by Romanians. Later the Wallachian prince Michael the Brave was able to, for a short time in 1600, unite the three regions, marking the first time this had ever been done under a single ruler. For this he is still today regarded as a symbol of Romanian unity.

In Transylvania, then under Habsburg rule, the cultural movement called the Transylvanian School was founded at a time when Romanians in the region faced social and political disenfranchisement. In the 1791 document Supplex Libellus Valachorum Transsilvaniae ("Petition of the Vlachs [Romanians] of Transylvania", the School demanded equal rights for the Romanian population and asserted a Romanian national continuity stretching back to Roman Dacia. The document was ignored.

The spread of Romantic nationalism throughout Europe in the 19th century affected the Romanians as well. The Wallachian uprising of 1821, led by Tudor Vladimirescu, has been described by scholars as espousing an early version of Romanian nationalism. American historian Grant T. Harward credits Vladimirescu's 1821 uprising with being "the first major sign of Romanian nationalism".

The closely related 1848 revolts in Wallachia and Moldavia (part of the broader European revolutions of 1848) also had nationalist overtones. Transylvanian Romanians during the Hungarian Revolution of 1848, led by Avram Iancu, fought the Hungarian revolutionaries and themselves demanded autonomy.

These nationalist currents ultimately culminated with the establishment of the personal union of Moldavia and Wallachia under Alexandru Ioan Cuza in 1859, which became a full political union in 1862 and established the modern Romanian state. It remained under Ottoman suzerainty, though this status was by then merely nominal. On 21 May 1877, Romania declared independence from the Ottomans in the midst of the Russo-Turkish War (1877–1878), with these events and the associated fighting known in Romanian historiography as the "Romanian War of Independence". Following the victory of the Russian Empire and Romania, the ruling prince Carol I assumed the title of King, reflecting the fully independent status of the country.

The Kingdom of Romania first expanded its territory with the acquisition of southern Dobruja from Bulgaria in 1913 during the Second Balkan War, which nonetheless only had a minority of Romanians.

The greatest and most important territorial expansion was initiated at the end of the First World War in 1918; the collapse of the Austro-Hungarian Empire allowed Transylvania to unite with Romania; and the collapse of the Russian Republic and the subsequent Russian Civil War allowed the Romanians of Bessarabia to set up the Moldavian Democratic Republic, which then proceeded to unite with Romania. "Greater Romania" was fulfilled, and the ambitions of the nationalists and irredentists were satisfied.