Marcus Vitruvius Pollio was a Roman architect, engineer, and author who lived during the 1st century BC. He is best known for his work "De architectura," a treatise on architecture, engineering, and urban planning. Vitruvius' writings have had a significant influence on the field of architecture and continue to be studied and referenced by architects and scholars to this day. He is also known for his theories on the proportions of the human body, which are often depicted in the famous drawing known as the "Vitruvian Man" by Leonardo da Vinci.