Polish–Lithuanian–Muscovite Commonwealth
The Polish–Lithuanian–Muscovite Commonwealth was a proposed state that would have been based on a personal union between the Polish–Lithuanian Commonwealth and the Tsardom of Russia. A number of serious attempts by various means to create such a union took place between 1574 and 1658 and in the late 18th century, but it never materialized because of the incompatible demands from both sides.
The proposed union is known in Polish as the Triple Union (unia troista) and has also been called the Polish–Russian Union (unia polsko-rosyjska) or the Polish–Muscovite Union (unia polsko-moskiewska).