Ilya Muromets (Russian: Илья́ Му́ромец; Ukrainian: Ілля́ Му́ромець, literally Elijah of Murom) is a Kievan Rus' epic hero. He is celebrated in numerous byliny (folk epic poems). Along with Dobrynya Nikitich and Alyosha Popovich he is regarded as the greatest of all the legendary bogatyrs (i.e., medieval knights-errant of Kievan Rus). (The three of them are represented together in Vasnetsov's famous painting Warriors, as illustrated below.)
Although Ilya's adventures are mostly a matter of epic fiction, he is believed to have been an historical person: a 12th century warrior and, in older age, a monk named Ilya Pechorsky. Ilya is beatified as a minor Saint of the Orthodox Church. His relics are preserved in the Kiev Pechersk Lavra.
Read more about Ilya Muromets: Ilya in byliny, Legendary Stature, Ilya As A Saint, Ilya Muromets Depictions