Universitas Valachorum (Estate of the Vlachs) is the Latin denomination for an Estate, an institution of self-government of the Romanians in medieval Transylvania.
The structure of the Universitas Valachorum placed the leadership of common Romanians upon their own nobility (Voivodes, Knez), enjoying a jurisdiction based on their own laws (Jus Valachicum). In the face of external danger such as Tatars, Cumans, Saracens and other pagans (omnino Tartarorum vel Cumanum Saracenum vel Meugarium) the Universitas of Romanians was called together with the other Estates of Transylvania (universisque nobilibus Ungarorum, Saxonibus, Syculis et Volachis) to defend Christian faith - Letter of Lodomerus, archbishop of Esztergom, 1288
When summoned by the king to the general assembly of Transylvania (congregatio generalis), Universitas Valachorum attended the assembly together with the other three Estates of Transylvania: Nobility, Saxons, and Székelys (Universis nobilibus, Saxonibus, Syculis et Olachis in partibus Transiluanis - András III summoning the assembly of Estates of Transylvania that took place on 22 February 1291).
The last known document attesting the Universitas Valachorum is dated May 1355, as the general assembly of the Estates (congregatio generalis) was summoned in Turda/Torda.
Insofar as a Romanian elite was preserved, it adjusted to these circumstances by converting to Roman Catholicism and being absorbed into Hungarian Catholic aristocratic estate (nobilis Hungarus). Those Romanian knezes (and voivods) who did not convert and could not gain the desired privileges gradually declined into the ranks of subjects or even bondsmen.
The last page of the history of Universitas Valachorum was written in 1437, as Transylvania witnessed the official establishment of the "brotherly union" or fraterna unio Unio Trium Nationum, that is, a community or gathering (universitas) of nobles, Saxons and Székelys, with the view of defending the country against the Ottoman threat and the inner danger of rebellious peasants. The adoption of the Unio Trium Nationum, which implicitly excluded the Estate of Romanians, gave constitutional sanction to the end of the Universitas Valachorum.