Inês Pérez de Castro (Inés in Spanish; 1325 – January 7, 1355) was a Galician noblewoman, daughter of Pedro Fernandez de Castro, lover and posthumously declared lawful wife of the Portuguese King Pedro I of Portugal, and therefore Queen of Portugal.

Inês came to Portugal in 1340 as a maid of princess Constance of Castile, recently married to prince Pedro, the heir to the throne. The prince fell in love with her and started to neglect his lawful wife, endangering the already feeble relations with Castile. Moreover, Pedro's love for Inês brought the exiled Castilian nobility very close to power, with Inês's brothers becoming the prince's friends and trusted advisors. King Afonso IV of Portugal, Pedro's father, disliked Inês's influence on his son and waited for their mutual infatuation to wear off, but it did not.

Constance of Castile died in 1349. Afonso IV tried several times to arrange for his son to be remarried, but Pedro refused to take a wife other than Inês, who was not deemed eligible to be queen. Pedro's legitimate son, future king Fernando I of Portugal, was a frail child, whereas Pedro and Inês's illegitimate children were thriving; this created even more discomfort among the Portuguese nobles, who feared the increasing Castilian influence over Pedro. Afonso IV banished Inês from the court after Constance's death, but Pedro remained with her. After several attempts to keep the lovers apart, Afonso IV ordered Inês's death. Pêro Coelho, Álvaro Gonçalves, and Diogo Lopes Pacheco went to the Monastery of Santa Clara in Coimbra, where Inês was detained, and killed her. Pedro rebelled against his father, causing civil war. The murder The murder

Pedro became king of Portugal in 1357. He then stated that he had secretly married Inês, who was consequently the lawful queen, although his word was, and still is, the only proof of the marriage. He had Inês's body exhumed and forced the entire court to swear allegiance to it as queen. She was later buried at the Monastery of Alcobaça where her coffin can still be seen, opposite Pedro's so that, according to the legend, at the Last Judgment Pedro and Inês can look at each other as they rise from their graves. Both marble coffins are exquisitely sculpted with scenes from their lives and a promise by Pedro that they would be together até ao fim do mundo (until the end of the world).

Inês de Castro’s history is immortalized in several plays and poems in Galician-Portuguese and Spanish language, including The Lusíadas by Luís de Camões and "Reinar despues de morir" by Luis Velez de Guevara.

There have been over 20 operas, including

   * Ines de Castro by Niccolò Antonio Zingarelli (1798)
   * Ines de Castro by Giuseppe Persiani to a libretto by Salvatore Cammarano (1835)
   * Ines de Castro by Scottish composer James MacMillan was first performed at the 1996 Edinburgh International Festival[1]
   * The opera Wut (Rage) in German by Swiss composer Andrea Lorenzo Scartazzini (born 1971) was performed for the first time at the Theater Erfurt, Germany, on September 9, 2006.

History of Inês de Castro in a cigarrete label.

Inês de Castro and Pedro I had the following children:

   * (Prince) Afonso (?), died young.
   * (Princess) Beatrice, (c. 1347–1381), married Sancho of Alburquerque aka Sancho of Castile, Count of Albuquerque & Haro.
   * (Prince) John (1349–1397), claimant to the throne during the 1383-1385 Crisis.
   * (Prince) Denis (1354–1397), claimant to the throne during the 1383-1385 Crisis.

Inês de Castro and Pedro I of Portugal were the great-great-grandparents of Ferdinand V of Castile. Ferdinard's wife Isabella of Castile was a great-great-granddaughter of Pedro I of Portugal and his mistress Teresa Lourenço.