Gesta Danorum is a patriotic work of Danish history, by the 12th-century author Saxo Grammaticus. It is the most ambitious literary undertaking of medieval Denmark and is an essential source for the nation's early history. It is also one of the oldest known written documents about the history of Estonia and Latvia.

Saxo Grammaticus, also known as Saxo cognomine Longus, was a Danish historian, theologian and author. He is thought to have been a clerk or secretary to Absalon, Archbishop of Lund, the main advisor to Valdemar I of Denmark. He is the author of the Gesta Danorum, the first full history of Denmark, from which the legend of Amleth would come to inspire the story of Hamlet by Shakespeare.