Diego Martínez de Villamayor, Castilian nobleman

Diego Martínez de Villamayor was a noble of the Kingdom of Castile from the house of the counts of Bureba, who was very influential at court. He was the advisor of Alfonso VII and Sancho III, and treasurer of Alfonso VIII.

The Kingdom of Castile was a polity in the Iberian Peninsula during the Middle Ages. It traces its origins to the 9th-century County of Castile, as an eastern frontier lordship of the Kingdom of León. During the 10th century, the Castilian counts increased their autonomy, but it was not until 1065 that it was separated from the Kingdom of León and became a kingdom in its own right. Between 1072 and 1157, it was again united with León, and after 1230, the union became permanent.