Ferdinand of Portugal, Lord of Eça

Ferdinand of Portugal (Portuguese: Fernando), later of Eça or Eza (c. 1378 – ?), was the son of Portuguese Infant João, Duke of Valencia de Campos. João, was a son of king Peter I of Portugal and Galician lady Inês de Castro, "the Queen who ruled after her death".

His father, Infante John, Duke of Valencia de Campos, had been legitimized as Infant of Portugal, and became duke of Valencia de Campos in Castile through his marriage to one of the bastards of King Henry II of Castile.

Fernando's father John, had married in 1376, (1st marriage), Portuguese lady Maria Téllez de Menezes, assassinated shortly after in 1378 by her husband, who had been alerted of her apparent unfaithfulness.

Then, he married again in Valencia de Campos in 1378 Constanza de Castilla, Lady of Valencia de Campos, illegitimate daughter of King Henry II of Castile.