The term Polish-Lithuanian Union refers to a series of acts and alliances between the Kingdom of Poland and the Grand Duchy of Lithuania that lead to the creation of the Republic of Both Nations in 1569 and eventually to creation of a unified state in 1791.

The most important acts of the union were:

• 1385 - Union of Krewo - personal union
• 1401 - Union of Vilnius and Radom - Lithuania granted vast authonomy with Vytautas as the Grand Duke and Władysław Jagiełło as his overlord
• 1413 - Union of Horodło -
• 1432 (1432-34) - Union of Grodno
• 1499 - Union of Vilnius
• 1501 - Union of Mielnik
• July 1, 1569 - Union of Lublin - creation of the Republic of Both Nations
• May 3, 1791 - May Constitution of Poland - both the Kingdom of Poland and Grand Duchy of Lithuania abolished and a common state created
• 1795 - Third Partition of Poland
• February 16, 1918 - Lithuania declares independence