Książę Siemowit III "Starszy" Prince of Mazovia

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Książę Siemowit III "Starszy" Prince of Mazovia (von Masowien)

Also Known As: "Ziemowit"
Birthplace: Of,Czersk,Bydgoszcz,Poland
Death: June 16, 1381 (56-65)
Czersk, Bydgoszcz, Poland
Place of Burial: Plock cathedral, Poland
Immediate Family:

Son of Książę Trojden I ks. Piast-Mazowiecki, książę and Księżna Maria of Galicia
Husband of Eufemie Opavská and Anna ziębicka of Munsterberg
Father of Anna; Eufemija Siemovitaitė; Janusz I Starszy ks. Piast-Mazowiecki, książę; Ziemowit von Masowien, Prince of Plock and Kujavia; Margaret of Masovia and 3 others
Brother of Boleslaus George II of Mazovia Yuri Piast, King of Mazovia; Eufemia Mazowiecka and Kazimierz I warszawski, książę

Occupation: Prins av Masovia
Managed by: Filip Jakub Łajszczak
Last Updated:

About Książę Siemowit III "Starszy" Prince of Mazovia

ZIEMOWIT III "Starszy" Prince of Mazovia

  • ZIEMOWIT of Mazovia, son of TROJDEN I Prince of Czersk [Piast] & his Maria Iurievna of Galich (before 1314-16 Jun 1381). He inherited Rawa in 1345 from his uncle Ziemowit II, jointly with his brother[539]. In 1355 he inherited the lands of his younger brother Kazimierz, but agreed to transfer all his holdings to Kazimierz III King of Poland who granted them back to Ziemowit as a Polish fief[540]. He succeeded in 1370 as ZIEMOWIT III "Starszy" Prince of Mazovia.


  • Married: firstly (1335) EUPHEMIA von Troppau, daughter of NIKOLAUS II Herzog von Troppau und Ratibor [P%C5%99emyslid] & his first wife Anna von Ratibor [Piast] ([1319]-before 11 Sep 1352).
  • Married: secondly (before 1365) --- Anna von Münsterberg, daughter of NIKOLAUS Herzog von Münsterberg [Piast] & his wife Agnes von Leuchtenberg ([1344/53]-[1368/72]).

Prince Ziemowit III & his first wife EUPHEMIA, had five children:

  • 1. EUPHEMIA ([21 Jun 1418/9 Dec 1424]). m (after [1367/69]) as his second wife, WLADISLAW Duke of Oppeln Palatine of Hungary, son of BOLESLAW II Duke of Oppeln [Piast] & his wife Elisabeth von Schweidnitz [Piast] ([1326/30]-8 or 18 May 1401).
  • 2. ANNA (before 1345-after 16 Mar 1403). Nun at Ratibor.
  • 3. JANUSZ (-8 Dec 1429). He succeeded in 1374 as JANUSZ I Prince of Ciechanów and Warsaw.
  • 4. MAŁGORZATA (before 1358-[14 May 1388/4 Apr 1396]). Her first marriage was arranged by her future husband's maternal grandfather, King Kazimierz III, as part of the agreement for the former's adoption by the king[541]. m firstly (Apr 1369) as his second wife, KASIMIR von Pommern, son of BOGISLAW V Duke of Pomerania in Hinterpommern & his first wife Elźbieta of Poland ([1351]-2 Jan 1377). He succeeded his father in 1373 as KASIMIR IV Duke of Pomerania in Stargard. m secondly (Jul 1379) as his second wife, HEINRICH VII Duke of Lüben and Brieg, son of LUDWIG I Duke of Brieg [Piast] & his wife Agnes von Glogau und Sagan [Piast] ([1343/45]-11 Jul 1399).
  • 5. ZIEMOWIT (before 1352-5 Dec 1425). He succeeded as Prince of Plock and Kujavia. m ([1387]) ALEKSANDRA of Lithuania, daughter of ALGIRDAS [Olgierd] Grand Duke of Lithuania & his second wife Iuliana Aleksandrovna of Tver [Rurikid] (-19 Jun 1434). Prince Ziemowit & his wife had twelve children:

Source - http://fmg.ac/Projects/MedLands/POLAND.htm#SiemowitIIIdied1381A

Siemowit remarried, after Euphemia's death to Anna, daughter of Nicolas of Ziębice. From this marriage he had three children:

  • unnamed son (1361/1364 - died young before 14 Mar 1378).
  • unnamed son (1362/1365 - died young before 14 Mar 1378).
  • Henry of Masovia (1368/1370–1392/1393), became Bishop of Płock.

Siemowit accused Anna of adultery when she became pregnant with Henry. After his birth Siemowit had Anna strangled and Henry cast away. However, it turned out Henry was the son of Siemowit so he was made a bishop.

After working his whole life on reuniting Masovia and making it an independent state, Siemowit III died on June 16, 1381 and was buried at Plock Cathedral.


iemowit III of Masovia (his name also rendered Ziemowit; c. 1320 – 1381) was a prince of Masovia and a co-regent (with his brother Casimir I of Warsaw) of the lands of Warsaw, Czersk, Rawa, Gostynin and other parts of Masovia.


Siemowit was the second son of Trojden I of Masovia and his wife Maria, daughter of Yuri I of Galicia.

In 1341, following the death of their father and brother, Siemowit and his younger brother Casimir inherited the Duchy of Czersk. In 1345 following the death of their uncle Siemowit II of Rawa, they also inherited the Duchy of Rawa. In 1349 the two brothers shared their possessions. Siemowit gave the small region of Warsaw to his brother Casimir, retaining the regions of Czersk, Liw and Rawa.

Early in his reign, Siemowit tried to establish good neighborly relations with his powerful neighbors: the Teutonic Order, Poland and Bohemia. Some historians believe that Siemowit rendered a tribute of vassalage to Charles IV, Holy Roman Emperor in 1346. Other historians say this happened in 1351, in order to inherit from Boleslaw III of Płock who was a vassal of Bohemia.

But on September 18, 1351, Siemowit and Casimir recognised the Polish King Casimir III the Great as suzerain, canceling the allegiance of Masovia and Bohemia. In exchange, they got Gostynin (Siemowit) and Sochaczew (Casimir), former possessions of Boleslaw III. Casimir also gave the Duchy of Płock to the brothers.

When his brother Casimir died unexpectedly in 1355, Casimir III the Great left the Duchy of Warsaw to Siemowit. In exchange, he promised never to ally with enemies of Poland and the Duchy of Płock would return to Poland, unless Casimir III died without an heir. In addition, Casimir III offered Siemowit a small territory of Lesser Poland bounded by the river Pilica and Radomka.

From that time, relations between Siemowit and Casimir III the Great become increasingly narrow. In 1363, Siemowit was invited to Krakow for the marriage of Elizabeth of Pomerania, granddaughter of the king of Poland, with the Emperor Charles IV. In September 1364 he participated in a conference in Krakow, which offered five crowned kings, dukes and princes extravagant festivities and tournaments. In 1369 Margaret, the daughter of Siemowit, wife of Casimir IV, Duke of Pomerania, adopted an illegitimate son of Casimir III the Great. At that time, Casimir IV of Słupsk was one of the contenders to succeed Casimir III the Great, who left only daughters.

When Casimir III the Great died in 1370, under agreements concluded with one of his lifetime friends Siemowit III, he freed Siemowit from Polish suzerainty and gave Płock, Wizna, Wyszogród and Zakroczym back to Mazovia. Having a reunified Masovia, it regained its independence, there Siemowit III promulgates a customary law in 1377. He reformed the administration, justice and the monetary system.

In 1373/1374 he gave the regions of Warsaw and Rawa to his sons, Siemowit IV of Masovia and Janusz I of Warsaw.


  • Siemowit III (Ziemowit) mazowiecki - od 1341 r. współrządził razem z bratem Kazimierzem I w Warszawie i Czersku, od 1345 w ziemi rawskiej, od ok. 1349 r. w wyniku podziału książę na Czersku, Liwie i Rawie, od 1351 r. w Gostyninie, od 1351 r. lennik króla Polski Kazimierza Wielkiego, od 1352 r. zastawny książę płocki, od 1355 r. w Warszawie i Sochaczewie, od 1370 r. władca suwerenny, także na Płocku, od 1370 w Zakroczymiu i Wiźnie, od 1373/4 wydzielił synom dzielnice w Warszawie i Rawie. http://pl.wikipedia.org/wiki/Siemowit_III
  • POLAND, Medieval Lands
  • Kazimierz Jasiński: Rodowód Piastów mazowieckich. Poznań - Wrocław 1998, p. 87-88.
  • Kazimierz Jasiński: Rodowód Piastów mazowieckich. Poznań - Wrocław 1998, p. 88-89.
  • (in Polish) Samuel Orgelbrand, Encyklopedja Powszechna, S. Orgelbranda Synów, p.54 (public domain via Google Print)
  • (in Polish) Józef Szujski, Historyi polskiéj treściwie opowiedzianéj ksiąg dwanaście, 1880, p.167, (public domain via Google Print)
view all 13

Książę Siemowit III "Starszy" Prince of Mazovia's Timeline

Of Czersk,Bydgoszcz,Poland
Czersk, Chojnice County, Pomeranian Voivodeship, Poland
Wyszogrod, Warszawa, Polen
Czersk, Pomorskie, Polska
Of Czersk,Bydgoszcz,Poland