Sigismund Kęstutaitis
Before 21 August 1439, Catherine married Michael Žygimantaitis, a Lithuanian prince and contender for the Grand Ducal throne as son of Sigismund Kęstutaitis, as his third wife. His two previous wives were also Masovian princesses: the first was Anna (Catherine's older sister) and the second was Euphemia (sister of Bolesław IV of Warsaw). They had no children.