The magnates of Poland and Lithuania were an of nobility (szlachta) that existed in the Crown of the Kingdom of Poland, in the Grand Duchy of Lithuania and, from the 1569 Union of Lublin, in the Polish–Lithuanian Commonwealth, until the Third Partition of Poland in 1795.
The magnate social class arose around the 16th century and, over time, gained more and more control over Commonwealth politics. The most powerful magnates were known as "little kings" due to the extent of their power and independence. Their influence diminished with the Third Partition of Poland (1795), which ended the Commonwealth's independent existence, and came to an end with the Second World War and the communist-ruled People's Republic of Poland.
Famous magnate families in the Crown of Poland territories included the Czartoryski, Kalinowski, Koniecpolski, Ostrogski, , Tarnowski, Wiśniowiecki, Zasławski and Zamoyski families; and in the Grand Duchy of Lithuania, the Kieżgajłow, Olelkowicz, Radziwiłł, Pac and Sapieha families.