OLGIERD (d. 1377), grand-duke of Lithuania, was one of the seven sons of Gedymin, grand-duke of Lithuania, among whom on his death in 1341 he divided his domains, leaving the young est, Yavnuty, in possession of the capital, Vilna, with a nominal priority. With the aid of his brother Kiejstut, Olgierd in drove out the incapable Yavnuty and declared himself grand duke. His reign (1345-1377) saw the development and extension of Lithuania to one of the greatest states in Europe of that time. The Teutonic knights in the north and the Tatar hordes in the south were equally bent on the subjection of Lithuania, while Olgierd's eastern and western neighbours, Muscovy and Poland, were far more frequently hostile competitors than serviceable allies. Olgierd not only held his own, but acquired influence and territory at the expense of both Muscovy and the Tatars, and extended the borders of Lithuania to the shores of the Black sea. He desired to establish the Lithuanian power in those Russian lands which had formed part of the ancient grand-duchy of Kiev. He procured the election of his son Andrew as prince of Pskov, and a powerful minority of the citizens of the republic of Nov gorod held the balance in his favour against the Muscovite influ ence, but his ascendancy in both these commercial centres was precarious. But he acquired the principalities of Smolensk and
Bryansk in central Russia. His relations with the grand-dukes of Muscovy were friendly, and twice he married orthodox Russian princesses; nevertheless, he besieged Moscow in 1368 and again in 1372, both times unsuccessfully.
Olgierd won a great victory over the Tatars at Siniya Vodui on the Bug in 1362, which practically broke up the great Kipchak horde and compelled the khan to migrate farther south and make his headquarters for the future in the Crimea. Indeed, but for the unceasing simultaneous struggle with the Teutonic knights, the burden of which was heroically borne by Kiejstut, Russian historians frankly admit that Lithuania, not Muscovy, must have become the dominant power of eastern Europe. Olgierd died in 1377, accepting both Christianity and the tonsure shortly before his death. His son Jagiello ultimately ascended the Polish throne, and founded the dynasty which ruled Poland nearly 2oo years.
See Kazimierz Stadnicki, The Sons of Gedymin (Pol.) (Lemberg, 1849-53) ; Vladimir Bonifatevich Antonovich, Monograph on the History of Western Russia (Rus.), vol. i. (Kiev, 1885).