Rollo (c.860 - c.932) was a Viking leader, probably (based on Icelandic sources) from Norway, the son of Ragnvald, Earl of Moer; sagas mention a Hrolf, son of Ragnvald jarl of Moer. However, the latinization Rollo has in no known instance been applied to a Hrolf, and in the texts which speak of him, numerous latinized Hrolfs are included. Dudo of St. Quentin (by most accounts a more reliable source, and at least more recent and living nearer the regions concerned), in his Gesta Normannorum, tells of a powerful Danish duke (or count?) at loggerheads with the king of Denmark, who then died and left his two sons, Gurim and Rollo, leaving Rollo to be expelled and Gurim killed.* With his followers (known as Normans, or northmen), Rollo invaded the area of northern France now known as Normandy.
Concluding the Treaty of Saint-Clair-sur-Epte (911) with the French king Charles the Simple, Rollo pledged feudal allegiance to the king, changed his name to the Frankish version, and converted to Christianity, probably with the baptismal name Robert. In return he was granted the lower Seine area (today's upper Normandy) and the titular rulership of Normandy, centred around the city of Rouen. There exists some argument among historians as to whether Rollo was a "duke" (dux) or whether his position was equivalent to that of a "count" under Charlemagne.
Sometime around 927 he passed the dukedom to his son, William Longsword. He may have lived for a few years after that, but certainly died before 933.
He was a direct ancestor of king William I of England.
See also: Ålesund, Viking Age