The Act of Mielnik or Union of Mielnik was an attempt to unite the Kingdom of Poland with the Grand Duchy of Lithuania in 1501. It was not ratified by the Lithuanian Seimas or by the Polish Sejm (see Łaski's Statute). The Act of Mielnik remained just a political project. Despite the failure to unify two countries into a single state, Poland and Lithuania were under a personal union until the Union of Lublin of 1569.