Saxo Grammaticus was a Danish historian and author who lived in the 12th century. He is best known for his work "Gesta Danorum," which is a comprehensive history of Denmark. Saxo Grammaticus' work is an important source for the history and legends of medieval Scandinavia. He is considered one of the most important chroniclers of early Danish history and his writings have had a significant impact on the understanding of the medieval period in Northern Europe.