Union of Krewo

In a strict sense, the Union of Krewo or Act of Krėva (also spelled Union of Krevo, Act of Kreva; Polish: unia w Krewie; Lithuanian: Krėvos sutartis) comprised a set of prenuptial promises made at Kreva Castle on 14 August 1385 by Jogaila, Grand Duke of Lithuania, in regard to his prospective marriage to the underage reigning Queen Jadwiga of Poland.

Though very limited in scope, the "Union of Krewo", in historiography, often refers not only to the particular document but to events of 1385–1386 as a whole.^[1] After the 1385 negotiations, Jogaila converted to Christianity, married Jadwiga, and was crowned King of Poland in 1386.

The union proved a decisive moment in the histories of Poland and Lithuania; it marked the beginning of four centuries of shared history of the two polities. By 1569 the Polish–Lithuanian union had developed into a new state, the Polish–Lithuanian Commonwealth, which lasted until the Third Partition of Poland in 1795.