In the first millennium BC, Slavs played a leading role in the development of civilization of ethno-Ukrainian society. In the new era Slavs expanded their territory greatly and they shared a common language, similar way of life, similar customs and beliefs. However, there were different tribes, each having its own chiefs, military and policy. Some of these groups are Scithians, Balts, Germans and Kerlates, which had influence on the ethnogenesis of Ukrainians. The intensive break-up of patriarchal traditions was observed in the 7th and 8th centuries in the development of East Slav society. Formation of social hierarchy began when property inequality of the community intensified.These processes were especially active in the territory of the Middle Dnipro Area and adjacent lands. Archeological sources have discovered rather quick development of arable farming, cattle rearing, handicrafts, and trade. Soon political and economic centers of Slavic tribes appeared, such as Kyiv. About 14 East Slav tribe unions existed in Ukraine during the 6th - 9th centuries. This lay the political groundwork for Rus. In the late 9th century, conditions appeared for forming early feudal states in the area of Slavic settlement. Modern Kyiv, Chernihiv and Pereiaslav were the centers of its territory.

Kyivan Rus'

In the year 882, Oleg, the Prince of Novhorod became the ruler of Kyiv or Old Rus, the first state of Old Slavs, which soon turned into one of the greatest countries of Medieval Europe and which played an important part in political life on the continent. Kyiv became the capital of the state. When he proclaimed Kyiv to be the political center of Rus, Prince Oleg (as well as his successors) were greatly concerned about the problem of consolidation of the nearest tribal principalities around Kyiv. All the East-Slav tribes and many non-Slav people were under dominion of the Kyiv Prince at the end of the 10th century. Kyiv Rus spread from the Black Sea to the White Sea, from the Carpathians to the Volga River. The vastness of the territory determined the availability of certain language and cultural peculiarities. The armed forces played the role of the state elite in Kyiv Rus until the early 11th century. Kyiv princes of the 9-10th centuries cared mainly about strengthening the economic and political power of the state. They fortified cities, put in order legal proceedings and a fiscal system, and regulated the obligations of the dependent population. During Princess Olga's reign (approximately 946), the first attempt was made to expel paganism and replace it with Christianity. But Christianity wasn't officially introduced as a state religion in Rus until 988 by Prince Volodymyr Sviatoslavych. Diplomatic relations of the Old Rus State with the neighboring countries, in particular, Byzanthia and the German Empire, intensified during the mid-10th century after the fall of Khozar's state.The military marches of Kyiv Princes played an important part in the expansion of the territory of Kyiv Rus and assertions of its power in the eyes of surrounding people. The creation of the Old Rus nation state took place during the reign of Prince Sviatoslav's son, Prince Volodymyr (978-1015). The economical and political strength of the state, the authority of the Prince's rule, and the organization of law considerably increased during his reign. The successful military raids of the Prince expanded the limits of the Rus territory.The process of forming the Old Rus State finished in the beginning of the 11th century under Yaroslav Mudriy.
From the 1130s the disintegration process of the Old Rus State attained an irreversible character. For several years, the territory of this newly powerful state was separated into several independent principalities whose owners did not stop military conflicts until the mid-13th century. The authority of the Kyiv Prince as the state head became quite formal but did not lead to the complete disintegration of the Old Rus state. Kyiv still remained its capital. The personal power of the Kyiv Prince was replaced by the government of "collective suzerainty" of the most influential and powerful Princes. A single centralized monarchy was changed into a federal monarchy, which no longer had the might nor size of its predecessor.
The period of feudal disintegration on the Old Rus lands not only set a mark on their political, socio-economic and cultural development, but also introduced certain innovations to geographical definitions of the state. In particular, the Kyiv Chronicle of 1187 had first coined the term "Ukraine" to define the southern area of Rus lands (Kyiv, Pereiaslav and Chernihiv provinces). After some time, this name was also applied to Halychyna, Volyn, and Podillia.