Duke of Masovia

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Dukes of Masovia in 1450

Duke of Masovia (Polish: Książę Mazowsza) was a title born by the sons and descendants of the Polish Duke Bolesław III Wrymouth. In accordance with the last will and testament of Bolesław, upon his death his lands were divided into four to five hereditary provinces distributed among his sons, and a royal province of Kraków reserved for the eldest, who was to be High Duke of all Poland. This was known as the fragmentation of Poland. Subsequent developments lead to further splintering of the duchies.

The following is a list of all rulers of the Duchy of Masovia and its parts. Although not all incumbents listed here had titular rights to the title of Duke of Masovia, they are all listed as such for simplicity's sake.

Also take note that some of the dates are merely approximate and the ownership of certain lands might be disputed. Finally, this table does not include lands ruled by dukes of other parts of partitioned Poland or Wenceslaus II and Wenceslaus III.

Duchy of Masovia[]

Partitions of Masovia[]

The Duchy went through various border changes in the coming years, sometimes losing and sometimes gaining territory.

Dukes of Masovia[]

Piast Dynasty[]

Ruler		Born	Reign	Death	Ruling Part	Consort	Notes
Boleslaus (I) the Curly		1125	1138-1173	5 January 1173	Masovia	Viacheslava Vsevolodovna of Novgorod 1138 three children Maria after 1160 no children	Son of Bolesław III Wrymouth of Poland. Also Duke of Silesia and monarch of Poland.
Leszek I		1162	1173-1186	1186	Masovia	Unmarried	Son of Bolesław the Curly.
Casimir (II) the Just		1138	1186-1194	5 May 1194	Masovia	1163 seven children	Son of Bolesław III Wrymouth of Poland. Also monarch of Poland.
Helena of Moravia-Znojmo (regent)		1141	1194-1200	1202/6	Masovia		Regent on behalf of her son.
Leszek II the White		1184/5		24 November 1227	Masovia	Grimislava Ingvarevna of Lutsk between 1208 and 1211 three children	Son of Casimir the Just. Also monarch of Poland, after his abdication of Masovia to his brother Conrad, in 1200, shortly after reaching majority.
Conrad I		1187/8	1200-1247	31 August 1247	Masovia	Agafia Yaroslavna of Peremyshl between 1207 and 1210 ten children	Son of Casimir the Just. Also monarch of Poland.
Boleslaus I		1208	1247-1248	25 February 1248	Masovia	1232 no children between 1245 and July 1247 no children	Son of Conrad I. Died without descendants.
Siemowit I		1224/8	1248-1262	23 June 1262	Masovia	1248 three children	Brother of Bolesław I. Killed in a battle against the Lithuanians, who also took his heir prisoner.
(regent)		Before 1248	1262-1264	12 April 1283	Masovia		Regents during Conrad's captivity in Lithuania.
Boleslaus, Duke of Greater Poland (regent)		1224/7		14 April 1279	Masovia	Yolanda of Hungary 1257 three children
Conrad II		1250	1264-1275	24 June or 21 December 1294	Masovia	Hedwig of Legnica 1265/70 one child	Released after two years of captivity. In 1275 divided the land with his brother Bolesław. After the division of the duchy he received Czersk. His death without male heirs allowed his brother to reunite the Duchy.
			1275-1294		Czersk
Boleslaus II		1253/8	1275-1294	20 April 1313	Płock	Gaudemantė Sophia of Lithuania 1279 three children Kunigunde of Bohemia 1291 (divorced 1302) two children	Reunited the duchy after the death of his brother, but after his own death Masovia was divided again.
			1294-1313		Masovia
Trojden I		1284/6	1310-1313	13 March 1341	Czersk	Maria Yurievna of Galicia-Volhynia 1309/10 four children	Son of Boleslaus II, retained Czersk during his father's lifetime. After Boleslaus' death, Trojden received more lands in inheritance and made Warsaw his new capital. Put his own son in the throne of Galicia-Volhynia.
			1313-1341		Warsaw
Siemowit II		1283	1313-1345	18 February 1345	Rawa	Unmarried	Son of Boleslaus II, retained Rawa. Left no descendants and his duchy was inherited by his nephews Siemowit III and Casimir I.
Wenceslaus I		1293/7	1313-1336	23 May 1336	Płock	1316 two children	Son of Boleslaus II, retained Płock.
Siemowit II, Duke of Rawa (regent)		1283	1336-1340	18 February 1345	Płock	Unmarried	Regents in name of their nephew, Bolesław III.
Trojden I, Duke of Warsaw (regent)		1284/6		13 March 1341	Płock	Maria Yurievna of Galicia-Volhynia 1309/10 four children
Boleslaus III		1322/30	1340-1351	20 August 1351	Płock	Unmarried	Son of Wenceslaus. In 1351 Płock was annexed by the Kingdom of Poland.
Annexation to the Kingdom of Poland (1351-1370)
Casimir I		1329/31	1341-1345	26 November/5 December 1355	Warsaw	Unmarried	Sons of Trojden I, ruled jointly. In 1345 inherited Rawa. In 1349 divided the land between them: Siemowit received Warsaw and Casimir Rawa. After Casimir's death without descendants in 1355, Siemowit reunited Masovia. He also brought Płock from Poland in 1370. After his death the duchy was again divided between his sons Janusz I and Siemowit IV.
			1345-1349		Warsaw and Rawa
			1349-1355		Rawa
Siemowit III		1320	1341-1345	16 June 1381	Warsaw	1335 five children c.1360 three children
			1345-1349		Warsaw and Rawa
			1349-1355		Warsaw
			1355-1381		Masovia
John I the Elder		1347/52	1381-1429	8 December 1429	Warsaw	Danutė Anna of Lithuania 1371/3 four children	Son of Siemowit III, since 1386 hereditary vassal of Poland, after 1391 Duke of Podlasie. Although the division, the duchy of Czersk remained annexed to the duchy of Warsaw.
Siemowit IV the Younger'		1353/6	1381-1426	21 January 1426	Płock and Rawa	Alexandra of Lithuania 1387 thirteen children	Son of Siemowit III. Since 1386, was an hereditary vassal of Poland, and, although having lost much of his domain to the Teutonic Order in 1382 (Wizna, Zawkrze, Płońsk), he gained other duchies (Bełz) from Poland.
Trojden II		1403/6	1426-1427	25 July 1427	Płock and Rawa	Unmarried	Sons of Siemowit IV, ruled jointly. In 1434 the three surviving brothers divided the land: Siemowit received Rawa, Casimir received Bełz, ad Ladislaus received Płock. The death of Siemowit and Casimir in 1442, both without descendants, allowed Ladislaus to reunite the inheritance of his father.
Siemowit V		1389	1426-1434	17 February 1442	Płock and Rawa	Between 15 October 1434 and 17 February 1437 one child
			1434-1442		Rawa
Casimir II		1401/3	1426-1434	15 September 1442	Płock and Rawa	Margareta Szamotuły 26 June 1442 no children
			1434-1442		Bełz
Ladislaus I		1406/9	1426-1434	11/12 December 1455	Płock and Rawa	1444 two children
			1434-1442		Płock
			1442-1455		Płock, Bełz and Rawa-Rawa
(regent)		c.1390?	1429-1436	3 May/1 August 1458	Warsaw	Bolesław Januszowic, heir of Warsaw 1412 three children	Daughter-in-law of Janusz I the Elder; Regent on behalf of her son.
Boleslaus IV		1421	1436-1454	10 September 1454	Warsaw	Barbara Olelkovna of Slutsk-Kapy 1440/5 ten children
		1410	1442-1459	5 July 1459	Rawa-Gostynin	Siemowit V Between 15 October 1434 and 17 February 1437 one child	Received Gostynin as her husband's inheritance. After her death her part rejoined Płock.
(regent)		1425?	1455-1459	After 15 August 1482	Płock and Rawa-Rawa	Władysław I 1444 two children	Regents on behalf of Anna's sons.
(regent)		1400		28 January 1463	Płock and Rawa-Rawa	Unmarried
Siemowit VI		2 January 1446	1459-1462	31 December 1461/1 January 1462	Płock and Rawa (Rawa and Gostynin)	Unmarried	Sons of Ladislaus I, ruled jointly. In 1459 inherited Gostynin from their aunt Margareta. After their deaths, Masovia was again reunited by the sons of Boleslaus IV.
Ladislaus II		After 31 October 1448		27 February 1462	Płock and Rawa (Rawa and Gostynin)	Unmarried
Barbara Olelkovna of Slutsk-Kapy (regent)		1421	1454-1462	10 September 1454	Warsaw	Bolesław IV 1440/5 ten children	Regents on behalf of Barbara's sons.
(regent)		1400		28 January 1463	Warsaw
Casimir III		10 June 1448/8 June 1449	1462	9 June 1480	Warsaw	Unmarried	Sons of Boleslaus IV, ruled jointly. In 1462 they inherited the rest of Masovia, reuniting the Duchy. However in 1471 they made new partitions: Casimir received Płock, however in 1475 abdicated of his lands to his brother Janusz, who hadn't any share of the land since 1471; Conrad received Czersk and Boleslaus Warsaw, which was reunited with Czersk by Conrad after Boleslaus' death in 1488. In 1495, as the last surviving brother in power, he reunited all Masovia definitely.
			1462-1471		Masovia
			1471-1475		Płock
Boleslaus V		c.1453	1462	27 April 1488	Warsaw	Anna Radzanów 20 July 1477 (morganatic, annulled 1480) no children
			1462-1471		Masovia
			1471-1488		Warsaw
John II		1455	1462	16 February 1495	Warsaw	Unmarried
			1462-1471		Masovia
			1475-1495		Płock
Conrad III the Red		1447/8	1462	28 October 1503	Warsaw	Magdaena Stawrot 1468/70 (morganatic) no children Unknown before 20 July 1477 (morganatic, divorced 1493?) no children Anna Radziwiłł between 29 September 1496 and 2 April 1497 four children
			1462-1471		Masovia
			1471-1488		Czersk
			1488-1495		Czersk and Warsaw
			1495-1503		Masovia
Anna Radziwiłł (regent)		1475/6	1503-1518	15 March 1522	Masovia	Conrad III between 29 September 1496 and 2 April 1497 four children	Regent in name of her children.
John III		27 September 1502	1518-1526	9/10 March 1526	Masovia	Unmarried	Sons of Conrad III, ruled jointly.
Stanisław I		17 May 1501	1518-1524	8 August 1524	Masovia	Unmarried
Anna		c.1498	1526	After 26 January 1557	Masovia	Stanisław Odrowąż 1536 one child	The last Masovian Piast. Sister of Stanislaus and John III. Anna was elected duchess by the nobles to maintain the independence of the Duchy. It was unsuccessful, because, in the same year, Masovia was annexed to the Kingdom of Poland.

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