1569 Union of Lublin
Under the terms of the 1569 Act of the Union of Lublin, the Kingdom of Poland and the Grand Duchy of Lithuania formed a single, federated state. As "a unique testimony to a voluntary union of two equal countries in the early modern age, the document was inscribed on UNESCO’s Memory of the World Register in 2018.
The document was hammered out by two equal sides in the course of protracted and turbulent negotiations. A combined parliament played a prominent role in creating the union and in its subsequent functioning. According to UNESCO, the Union of Lublin and the imultiethnic and multicultural Polish-Lithuanian Commonwealth it created, was the high point of the Jagiellonian monarchy.
The Act united its constituent nations by means of a common sovereign, a shared Sejm, a common currency, as well as shared foreign and defence policies. The union survived until the late 18th century, when its lands were gradually seized by Russia, Prussia and Austria in three rounds of partitions.
Poland, Lithuania, Latvia, Belarus and Ukraine had jointly submitted the Act of the Union of Lublin for inscription on the Memory of the World Register, which protects the world's documentary heritage. The inscribed document is in Polish, and was issued by the Grand Duchy of Lithuania to the Polish side. It is kept at the Central Archives of Historical Records in Warsaw, whereas the copy presented to the Lithuanian side by the Crown went missing.