Morlachs (in Greek: Mavrovlachi or Mauro-Vlachs, meaning "Black Vlachs"; in Latin sources: Nigri Latini) were a population of Vlach (Romanian and possibly Romanized Illyrians) shepherds that lived in the Dinaric Alps (western Balkans in modern use), constantly migrating in search for better pastures for their sheep flocks.

The adjective "black" is used here with the meaning of "Northern", as opposed to the "white" Southern Vlachs of Macedonia and Greece.

Reports of the mid-11th century suggest that they lived in the mountainous regions of Montenegro, Bosnia (Stara Vlaška ), Herzegovina and on the Dalmatian coast. In the 14th century, some Morlachs moved northward and settled in Croatia and in particular later where they served as frontier guardians in the Military Frontier between Austria (Croatia) and Turkey (Bosnia). The continuous attempts of feudal lords to reduce them to serfs have failed. It is not quite clear as yet how Morlachs have made it but the slower feudalization of the Western Balkans compared to the West Europe and the Ottomans' conquering with Morlachs' lifelong military border services to both Turks and Austrians seem to alleviate their keeping out of the feudal bonds. Greater freedom and easier movability have given rise to the continuous running Slavic serfs over to them, and eventually most Morlachs were linguistically assimilated to Slavs.

The first phase of that proactive assimilation of Morlachs took place in Herzegovina and Montenegro where they not only were accepting the language of the Red Croats, but also turning it into a new Slavic language "novoshtokavian" which later on served as the base of Serbo-Croatian. But the fact that the Morlachs in the Western Balkan never reached the level of a nation, and have not given it their proper name resulted in recent disintegration of the Serbo-Croatian into Bosnian, Croatian and Serbian language.

By the 15th century, the nonassimilated Morlachs reached Istria, where now their descendents are now Istro-Romanians. Another group reached the island of Krk around 1450 and settled in the villages of Dubasnica and Poljica, where until the 19th century the people spoke a language that was a mix of Romanian and Slavic words.

Also their name was used for the populations of the mountains up to the 19th century. The terms Vlachs/Morlachs and Serbs were virtually indistinguishable in some contexts, causing noticeable confusion in some history books.

It has been suggested that the Bunjevci and Sokci are in fact Croatized Catholic Morlachs who speak so called ikavian novostokavian (mliko = milk) unlike the modern Serbs (Orthodox Morlachs) in Croatia, Bosnia and Herzegovina and Stari Vlah who speak iekavian novostokavian (mlijeko = milk).

References

• Danubian Europe: Maurovalachia