Ruthenia in the context of "Kamianets-Podilskyi Castle"

The history of Christianity in Ukraine dates back to the earliest centuries of the history of Christianity, to the Apostolic Age, with mission trips along the Black Sea and a legend of Andrew the Apostle even ascending the hills of Kiev. The first Christian community on territory of modern Ukraine is documented as early as the 4th century with the establishment of the Metropolitanate of Gothia, which was centered in the Crimean peninsula. However, on territory of the Old Rus in Kiev, Christianity became the dominant religion since its official acceptance in 989 by Vladimir the Great (Volodymyr the Great), who brought it from Byzantine Crimea and installed it as the state religion of medieval Kievan Rus (Ruthenia), with the metropolitan see in Kiev.

Although separated into various Christian denominations, most Ukrainian Christians share a common faith based on Eastern Christianity. This tradition is represented in Ukraine by the Byzantine Rite, the Eastern Orthodox and Eastern Catholic churches, which have been at various historic times closely aligned with Ukrainian national self-identity and Byzantine culture.

Ukrainians (Ukrainian: українці, romanised: ukraintsi, pronounced [ʊkrɐˈjin⁽ʲ⁾ts⁽ʲ⁾i]) are an East Slavic ethnic group native to Ukraine. Their native tongue is Ukrainian, and the majority adhere to Eastern Orthodoxy, forming the second largest ethno-linguistic community. At around 46 million worldwide, Ukrainians are the second largest Slavic ethnic group after Russians.

Ukrainians have been given various names by foreign rulers, which have included Polish–Lithuanian Commonwealth, the Habsburg monarchy, the Austrian Empire, and then Austria-Hungary. The East Slavic population inhabiting the territories of modern-day Ukraine were known as Ruthenians, referring to the territory of Ruthenia; the Ukrainians living under the Russian Empire were known as Little Russians, named after the territory of Little Russia.

Western Ukraine or West Ukraine (Ukrainian: Західна Україна, romanized: Zakhidna Ukraina, IPA: [ˈzɑxidnɐ ʊkrɐˈjinɐ]) refers to the western territories of Ukraine. There is no universally accepted definition of the territory's boundaries, but the contemporary Ukrainian administrative regions (oblasts) of Chernivtsi, Ivano-Frankivsk, Lviv, Ternopil and Zakarpattia (which were part of the former Austro-Hungarian Empire) are typically included. In addition, Volyn and Rivne oblasts (parts of the territory annexed from the Polish–Lithuanian Commonwealth during its Third Partition) are also usually included. In modern sources, Khmelnytskyi Oblast is often included because of its geographical, linguistic and cultural association with Western Ukraine, although this cannot be confirmed from a historical and political point of view. It includes several historical regions such as Carpathian Ruthenia, Halychyna including Pokuttia (the eastern portion of Eastern Galicia), most of Volhynia, northern Bukovina and the Hertsa region, and Podolia. Western Ukraine is sometimes considered to include areas of eastern Volhynia, Podolia, and the small northern portion of Bessarabia.

The area of Western Ukraine was ruled by various polities, including the Kingdom of Galicia–Volhynia, which became part of the Polish–Lithuanian Commonwealth, but also the Principality of Moldavia; it would then variously come under rule of the Austrian Empire, Austria-Hungary, the Second Polish Republic, the Kingdom of Romania, and finally the Soviet Union (via the Ukrainian Soviet Socialist Republic) in 1939 and 1940 following the invasion of Poland and the Soviet occupation of Bessarabia and Northern Bukovina, with the borders finalized after the end of World War II. After the dissolution of the Soviet Union, it became part of the independent Ukrainian state.

Red Ruthenia, also called Red Rus' or Red Russia, is a term used since the Middle Ages for the south-western principalities of Kievan Rus', namely the Principality of Peremyshl and the Principality of Belz. It is closely related to the term Cherven Cities ("Red Cities").

First mentioned by that name in a Polish chronicle of 1321, Red Ruthenia was the portion of Ruthenia incorporated into Poland by Casimir the Great during the 14th century. Following the Mongol invasion of Kievan Rus' in the 13th century, Red Ruthenia was contested by the Grand Duchy of Lithuania (the Gediminids), the Kingdom of Poland (the Piasts), the Kingdom of Hungary and the Kingdom of Galicia–Volhynia. After the Galicia–Volhynia Wars, for about 400 years, most of Red Ruthenia became part of Poland as the Ruthenian Voivodeship.

The Galicia–Volhynia Wars were several wars fought in the years 1340–1392 over the succession in the Kingdom of Galicia–Volhynia, also known as Ruthenia. After Yuri II Boleslav was poisoned by local Ruthenian nobles in 1340, both the Grand Duchy of Lithuania and the Kingdom of Poland advanced claims over the kingdom. After a prolonged conflict, Galicia–Volhynia was partitioned between Poland (Galicia) and Lithuania (Volhynia) and Ruthenia ceased to exist as an independent state. Poland acquired a territory of approximately 52,000 square kilometres (20,000 sq mi) with 200,000 inhabitants.

The Principality of Smolensk (eventually Grand Principality of Smolensk) was a Ruthenian lordship from the 11th to the 16th century. Until 1127, when it passed to Rostislav Mstislavich, the principality was part of the land of Kiev. The principality gradually came under Lithuanian influence and was incorporated into the Grand Duchy of Lithuania in 1404. The principality was reorganized into the Smolensk Voivodeship in 1508. The Principality of Moscow controlled the city from 1514 to 1611, then it was recaptured by the Polish–Lithuanian Commonwealth. The Tsardom of Russia recaptured the city in 1654.

The Principality of Vitebsk (Belarusian: Віцебскае княства) was a Ruthenian principality centered on the city of Vitebsk in modern Belarus, that existed from its founding in 1101 until it was nominally inherited into the Grand Duchy of Lithuania in 1320. Vitebsk would later fall under the complete authority of Lithuania in 1508.

The history of Lithuania dates back to settlements founded about 10,000 years ago, but the first written record of the name for the country dates back to 1009 AD. Lithuanians, one of the Baltic peoples, later conquered neighboring lands and established the Grand Duchy of Lithuania in the 13th century (and also a short-lived Kingdom of Lithuania). The Grand Duchy was a successful and lasting warrior state. It remained fiercely independent and was one of the last areas of Europe to adopt Christianity (beginning in the 14th century). A formidable power, it became the largest state in Europe in the 15th century spread from the Baltic Sea to the Black Sea, through the conquest of large groups of East Slavs who resided in Ruthenia.

In 1385, the Grand Duchy formed a dynastic union with Poland through the Union of Krewo. Later, the Union of Lublin (1569) created the Polish–Lithuanian Commonwealth. During the Second Northern War, the Grand Duchy sought protection under the Swedish Empire through the Union of Kėdainiai in 1655. However, it soon returned to being a part of the Polish–Lithuanian state, which persisted until 1795 when the last of the Partitions of Poland erased both independent Lithuania and Poland from the political map. After the dissolution, Lithuanians lived under the rule of the Russian Empire until the 20th century, although there were several major rebellions, especially in 1830–1831 and 1863.