In the historical demographics the largest earlier shock was the Mongol Invasion of Hungary, several plagues also took a toll on the country's population.

According to demographers, about 80 percent of the population was made up of Hungarians before the Battle of Mohács, however the Hungarian ethnic group became a minority in its own country in the 18th century due to centuries long Ottoman and Habsburg wars, the resettlement policies and continuous immigration from neighboring countries.

The percentage and the absolute number of all non-Hungarian nationalities decreased in the next decades, although the total population of the country increased.

Note: 300.000 Hungarian refugees fled to Hungary from the territory of successor states (Romania, Czechoslovakia and Yugoslavia) after the WW I.

After these population movements Hungary became an ethnically almost homogeneous country except the rapidly growing number of Romani people in the second half of the 20th century.

For historical reasons, significant Hungarian minority populations can be found in the surrounding countries, notably in Ukraine (in Transcarpathia), Slovakia, Romania (in Transylvania), and Serbia (in Vojvodina).

Written sources from the 9th century also suggest that some groups of Onogurs and Bulgars occupied the valley of the river Mureș at the time of the Magyars’ invasion.

During the centuries they were fully assimilated to the Hungarian population, their language disappeared, but they preserved their Jassic identity and their regional autonomy until 1876.

Regardless of the subject of Romanian presence/non-presence in Transylvania prior to the Hungarian conquest, the first chronicles to write of Vlachs in the intra-Carpathian regions is the Gesta Hungarorum,[136][137] while the first written Hungarian sources about Romanian settlements derive from the 13th century, record was written about Olahteluk village in Bihar County from 1283.

[138][139] The 'land of Romanians', Terram Blacorum (1222, 1280)[139][140][141][142] showed up in Fogaras and this area was mentioned under different name (Olachi) in 1285.

According to a research based on place-names made by István Kniezsa, 511 villages of Transylvania and Banat appear in documents at the end of the 13th century, however only 3 of them bore Romanian names,[143] and around 1400 AD, Transylvania and Banat consisted of 1757 villages, though only 76 (4.3%) of them had names of Romanian origin.

[145] Jean W. Sedlar estimates that Vlachs (Romanians) constituted about two-thirds of Transylvania's population in 1241 on the eve of the Mongol invasion,[146] however according to Károly Kocsis and Eszter Kocsisné Hodosi the Hungarian ethnic group in Transylvania was in decent majority before Battle of Mohács and only lost its relative majority by the 17th century.

[149][150][151] In 1881, Romanian-majority settlements projected to the present-day territory of Hungary were: Bedő, Csengerújfalu, Kétegyháza, Körösszakál, Magyarcsanád, Méhkerék, Mezőpeterd, Pusztaottlaka and Vekerd.

[152] Important communities lived in the villages of Battonya, Elek, Körösszegapáti, Létavértes, Nyíradony, Pocsaj, Sarkadkeresztúr, Zsáka and in the town of Gyula.

Due to post-Ottoman resettlements, the regions of Vojvodina, Banat and Békés county received bigger Slovak communities in the 18th century, which revitalized many deserted villages and towns, such as Békéscsaba, where Slovaks became the biggest ethnic group, or Nyíregyháza, where they comprised more than a third of the population in 1881.

SerbsFrom the 14th century, escaping from the Ottoman threat, a large number of Serbs migrated to the Hungarian Kingdom.

After the Turkish withdrawal, Kingdom of Hungary came under Habsburg rule, a new wave of Serb refugees migrated to the area around 1690, as a consequence of the Habsburg-Ottoman war.

The third, largest wave of German-speaking immigrants into Hungary occurred after the withdrawal of the Ottoman Empire from Hungarian territory, after the Treaty of Karlowitz.

At the end of the 18th century, the Kingdom of Hungary contained over one million German-speaking residents (collectively known as Danube Swabians).

Croat communities were spread mostly in the western and southern part of the country and along the Danube, including Budapest.

Mass migrations did not occur until the 17th century,[163] the largest waves being in 1718 and 1760–1770;[164] they were primarily connected to the economic conditions of the period.

Hungary remained predominantly Catholic until the 16th century, when the Reformation led to the first Lutherans, and later Calvinists, which were embraced by nearly the entire Hungarian population at the time.

In the second half of the 16th century, Jesuits led a successful campaign of counterreformation among the Hungarians, although Protestantism survived as the faith of a significant minority, especially in the far east and northeast of the country.

Orthodox Christianity in Hungary has been the religion mainly of some national minorities in the country, notably Romanians, Rusyns, Ukrainians, and Serbs.