Today the historical territory of Rus, in the broadest sense, forms part(s) of the territories of Ukraine, Belarus, Russia, a small part of north-eastern Slovakia and a narrow strip of eastern Poland.
Due to the continuous political instability of this territory, the term Ruthenia may mean significantly different things, depending on who applies this term, when, why and to which period.
The term "Ruthenia" may refer to one or more of the following entities, appearing roughly in chronological order:
If the name Ruthenia has any connection to the name Rus, it is in the west generally held to derive from the Varangians whom the early Slavic and Finnic tribes called Rus' and this name is derived from the Old Norse root rođs- or roths- referring to the domain of rowing and still existing in the Finnish and Estonian names for Sweden, Ruotsi and Rootsi. Later the name came to denote not only the Scandinavian aristocracy in Eastern Europe but also the ethnically mixed population of their domains.
Some modern scholars use the spelling Ruthenia when discussing the Middle Ages in English texts. However, the ancient state of Rus did not have a proper name apart from the phrase zemlya ruskaya, and therefore there were different spellings in different languages.
The term Ruteni first appears in the form rex Rutenorum in the 12th-century Augsburg Annals. It was most likely a reflex of the ancient tradition, when the barbaric people were called by the names found in Classical Latin authors, i.e. Danes were called Daci and Germans were called Theutoni. Likewise, the Rus passed by the name of Ruteni, the form being influenced by one of the Gallic tribes mentioned by Julius Caesar.
There is a 12th-century Latin geography from France which says that "Russia is also called Ruthenia, as you may see from the following phrase of Lucan…" The original Latin text: Polonia in uno sui capite contingit Russiam, quae et Ruthenia, de qua Lucanus: Solvuntur flavi longa statione Rutheni. Earlier the Rus had been referred to as Rugi (one of the foremost Gothic tribes) and Rutuli (an Italic tribe mentioned by Virgil in the Aeneid).
By the end of the 12th century, the word Ruthenia was used, among the alternative spelling Ruscia and Russia, in Latin papal documents to denote the lands formerly dominated by Kiev. By the 13th century, the term became the dominant name for Rus' in Latin documents, particularly those written in Hungary, Bohemia, and Poland.
The territories of Halych-Volynia in the south fell under Catholic Lithuanian and Polish influence, and therefore were usually denoted by the Latin Ruthenia, because the Pope preferred this spelling. He used it, for example, when he proclaimed one of the local princes "King of Ruthenia". However, other spellings were used in Latin, English and other languages during this period as well.
These southern territories have corresponding names in Polish:
A notable exception occurred shortly after World War II, in relation to Belarusians from the Kresy region of pre-WWII Poland who found themselves in displaced persons camps in the Western occupation zones of the post-war Germany. At that time the notion of a Belarusian nation met with little recognition in the West. Therefore, to avoid confusion with the term "Russian" and hence "repatriation" to the Soviet Union (which finalized the annexion of Kresy after the war), the terms White Ruthenian, Whiteruthenian, and Krivian were used. The last of these terms derives from the name of an old Eastern Slavic tribe called the Krivichs, which used to inhabit the territory of Belarus.
From 1840 on, nationalists encouraged people to give up the name "Little Rus" for Ukrayina.
In the 1880s and 1900s, due to the spread of the name "Ukraine" as a substitute for "Ruthenia" among the Ruthenian/Ukrainian population of the Russian Empire, the name, "Ruthenian" was often restricted to mean western Ukraine, an area then part of the Austro-Hungarian state.
In the early 20th century, the name "Ukraine" was widely accepted in Galicia/Halychyna and the name "Ruthenia" became narrowed to the area south of the Carpathian Mountains in the Kingdom of Hungary. Carpathian Ruthenia incorporated the cities of Mukachiv/Mukachevo/Munkács, Uzhhorod/Ungvár and Presov/Pryashiv/Eperjes. This area had been part of the Hungarian kingdom since the late 11th century, and had been known as "Magna Rus'", but was also called "Karpato-Rus'" or "Zakarpattya" (see Carpathian Ruthenia).
After being incorporated into Czechoslovakia between World War I and World War II, the area tried to declare its independence as "Carpatho-Ukraine" at the dawn of World War II. The English term Rusyn arose around this time for the nationality and language of three groups of montagnards in the Carpathians. The name "Ruthenia" became largely identical with Carpathian Ruthenia, i.e. mostly the westernmost region of present-day Ukraine.
A Ruthenian minority also remained in northeastern Czechoslovakia (now Slovakia) after World War II. The people of the region rapidly became Slovakicised, because their language is closely related to the Slovak language and because most of them refused to identify themselves as Ukrainians, as the Communist government, after 1953, wished them to do.