Masovia was conquered probably by Mieszko I, duke of Polanes and first historical ruler of Poland in the 10th century.
During the chaos following the death of Mieszko II in 1033 and the subsequent invasion of the Czechs, it split temporarily from Poland under an independent ruler. It was then subdued by Casimir I of Poland in 1039 with help from Ruthenian units.
Following fragmentation of Poland after death of Boleslaus III of Poland Masovia was governed by his son Boleslaus IV of Poland, later high-duke of Poland 1146-1173 and other dukes from the local branch of the Piast dynasty. Some parts of Masovia were not incorporated into the Polish kingdom united in 14th century until death of the last regional duke in 1526.
Following the partitions of Poland Masovia became part of Congress Kingdom (1815) and later the Russian Empire (1831). In 1918 Masovia was included into newly formed Poland.
In 1997 there was created the Masovian Voivodship as one of 16 administrative regions of Poland.
History
Also a name of an early 8-bit character encoding, based on CP 850 with some characters replaced by Polish diacritics.