Count of Trastámara

The Count of Trastámara (Condado de Trastámara ) is a noble title granted by Juan II of Castile to Pedro Álvarez Osorio on the 4 February 1445 in San Martín de Valdeiglesias. Its name comes from the Latin Tras Tamaris, referring to the Tambre, a river which runs through Galicia. The title of Earl of Trastámara had previously been granted for life to others, including Alvar Núñez Osorio and future Enrique II of Castile, founder of the House of Trastámara.