The Jagiellonians were a royal dynasty that ruled over several Central and Eastern European countries from the late 14th to the 16th centuries. They originated from the Grand Duchy of Lithuania and expanded their influence through strategic marriages and alliances, notably with the Kingdom of Poland. This union led to the establishment of the Polish-Lithuanian Commonwealth, a significant political entity in Europe. The dynasty is named after Jogaila, who became King of Poland in 1386. The Jagiellonians played a crucial role in the cultural and political development of the region, promoting Renaissance ideas and strengthening ties between different nations. Their reign marked a period of prosperity and territorial expansion.