| Alexandra of Lithuania | |
| Duchess consort of Masovia | |
| Noble Family: | Gediminids (by birth) House of Piast (by marriage) |
| Father: | Algirdas |
| Mother: | Uliana of Tver |
| Spouse: | Siemowit IV, Duke of Masovia |
| Issue: | Kazimierz II of Masovia Trojden II of Masovia Władysław I of Płock Siemowit V of Masovia Alexander of Masovia Euphemia of Masovia Cymburgis of Masovia Jadwiga of Masovia Amelia of Masovia Anna of Masovia Maria of Masovia Alexandra of Masovia Catherine of Masovia |
| Birth Date: | late 1360s or early 1370s |
| Death Place: | Płock |
Alexandra (Polish: Aleksandra, Lithuanian: Aleksandra; died 20 April 1434 in Płock)[1] was the youngest daughter of Algirdas, Grand Duke of Lithuania, and his second wife, Uliana of Tver.[2] Though Alexandra's exact date of birth is not known, it is thought that she was born in the late 1360s or early 1370s. In 1387, she married Siemowit IV, Duke of Masovia, and had thirteen children with him.
On 12 December 1385, few months after the Union of Krewo, Siemowit IV, Duke of Masovia, reached a compromise with Queen Jadwiga of Poland and her intended consort, King Jogaila (Władysław II Jagiełło), the brother of Alexandra. Siemowit IV agreed to cease his rival claims to the Kingdom of Poland, pay homage to Jadwiga and Jogaila, and to assume the position of a hereditary vassal to the Polish crown in exchange for 10,000 Prague groschen and a fief (the Duchy of Belz). The agreement was solidified by the marriage of Siemowit IV and Alexandra in 1387.[3]
Alexandra died at the age of about 65 and was buried in Płock. Her final resting place is likely a church of the Dominican Order.[4]
Alexandra was frequently pregnant during her union with Siemowit, giving birth to 13 children- five sons and eight daughters- in about 25 years.
Grandchildren of Alexandra and Siemowit IV included Frederick III, Holy Roman Emperor, Przemyslaus II, Duke of Cieszyn, Sophie of Pomerania, Duchess of Pomerania and Dorothy Garai.
Karol Piotrowicz, w: Polski Słownik Biograficzny/ Polish Biographical Dictionary. T. 1. Kraków: Polska Akademia Umiejętności – Skład Główny w Księgarniach Gebethnera i Wolffa, 1935, p. 66–67
. Kazimierz Jasiński (historian) . Rodowód Piastów mazowieckich . 1998 . Wydawnictwo Historyczne . Poznań – Wrocław . 83-913563-0-2 . 90 .