Garci Lasso de la Vega I, also known as "el Viejo" (d. 1326, Soria) was a Spanish noble in the service of King Alfonso XI of Castile. He was the chancellor of the Kingdom of Castile, an adelantado of the King. He later became the chief justice of the King and gained vast properties in Asturias de Santillana and feudal land tenures and vassal towns in more than fifteen areas throughout Castile. He went to Soria in 1326 to recruit allies against infante Don Juan Manuel who had been consistently violating the King's territories. The Spanish nobles of Soria assaulted him with crossbows, driving Juan Manuel to seek cover at the Convent of San Francisco where he was eventually killed. Alfonso XI punished all those responsible, ordering their execution.