Princess Beatrice of Portugal (in Portuguese Beatriz (1372, Coimbra-1410)) was the daughter of king Fernando of Portugal and his wife, the Castilian Leonor Telles de Menezes.
In the beginning of 1383, the political situation in Portugal was not peaceful. Beatrice was the king's only child, and heir to the throne, after her younger brothers' deaths in 1380 and 1382. Her marriage was the political issue of the day and inside the palace, factions lobbied constantly. Ferdinand arranged and cancelled his daughter's wedding several times before settling for his wife's first choice, king Juan I of Castile. Juan had lost his wife (Princess Leonor of Aragon) the year before, and was happy to take the Portuguese heiress. The wedding took place on May 17, 1383 in the Portuguese city of Elvas. Beatrice was only eleven years old -- old enough, apparently, for a marriage in the 14th century.
King Ferdinand of Portugal died shortly thereafter, on October 22, 1383. According to the treatise between Castile and Portugal, the Queen Mother, Leonor Telles de Menezes, became regent in the name of her daughter and son-in-law. But not everybody in Portugal was happy about this state of affairs. The loss of independence was unthinkable for the majority of Portuguese nobles. A rebellion led by the Master of the Order of Aviz, future Joćo I of Portugal started in that year, leading to the 1383-1385 Crisis.
Juan I of Castile invaded Portugal in 1384 to fight for his newly-born son Miguel's (1384-1385) rights to the crown. That war ended in the next year, with the utter defeat of Castile in the Battle of Aljubarrota. In the aftermath of this battle, Joćo I of Aviz became the uncontested king of Portugal. Beatrice was no longer heir to the throne; she was merely the Consort Queen.