Beatrix of Portugal was a Portuguese princess born in 1373, the daughter of King Ferdinand I of Portugal and Queen Leonor Teles. She became the Queen of Castile through her marriage to John I of Castile in 1383. This union was significant as it aimed to strengthen ties between Portugal and Castile during a tumultuous period. Beatrix's marriage led to the Portuguese Crisis of 1383-1385, a conflict over the Portuguese throne. After her husband's death, she was involved in the political struggles that ensued, ultimately leading to the rise of John I of Portugal, who became the first king of the Aviz dynasty.