King Ferdinand I of Portugal reigned from 1367 to 1383. He was the son of King Pedro I of Portugal and Inês de Castro. His rule was marked by political instability and conflicts with neighboring kingdoms, particularly Castile. Ferdinand's inability to produce a male heir led to a succession crisis. Ferdinand I's death in 1383 sparked the Portuguese succession crisis, which ultimately resulted in the ascension of John I of Portugal. This period was crucial in shaping the future of Portugal, leading to the establishment of the Aviz dynasty and significant developments in Portuguese exploration.