Vladimir I was the son of
Sviatoslav I of Russia, and came to power there about
980 after overthrowing his older brother
Yaropolk I. He had fled to Scandinavia when his father died and civil war broke out between his brothers, but the people of the city of
Novgorod invited Vladimir to come back and rule them. He not only did that but managed to conquer
Kiev and have Yaropolk executed.
Like his predecessors, he made conquests to expand the territory of Kievan Russia, and recover lands that had been taken over by other kingdoms such as Poland; he started many cities in these lands. At first he also built many pagan temples with large idols to intimidate the opposition. However, he is most remembered for converting Russia to Christianity, and has the nickname "the Saint" (he has been canonized by the Russian Orthodox Church).
Some scholars credit his marriage to the sister of the Byzantine emperor with Vladimir's conversion (though he had other wives and ended up with about twelve sons); however, he had to send troops to prevent the emperor from breaking the betrothal. There is also a legend that he sent for representatives of several religions, but refused to convert to Judaism because their religion had no homeland; was not interested in Islam once he found out it would forbid him to drink alcohol; and eventually chose Orthodox Christianity because his ambassadors to Constantinople told him that the church rituals were beautiful and impressive. However he came to that conclusion, by 989 he was building Christian churches in Kiev and having his subjects forcibly baptized. This choice had a lot of influence on the future of Russia, especially its future conflicts with its neighbor, Catholic Poland.
Nonetheless, Vladimir continued fighting with neighboring tribes and sending his sons to govern his new cities. He died in 1015, and a civil war between his sons ensured; the first one to succeed him was Sviatopolk I.