William de Lacy, Baron de Lacy, was a notable figure in medieval England, known for his role as a landowner and nobleman. He held significant estates in Yorkshire and was a prominent supporter of the Norman Conquest in the 11th century. His lineage can be traced back to the de Lacy family, which played a crucial role in the governance and military affairs of the time. As a baron, William de Lacy was responsible for managing his lands and overseeing the local populace. He participated in various military campaigns and was involved in the feudal system, which defined the social and political structure of medieval England. His contributions helped shape the landscape of the region during his lifetime.