• Norman adventurer remembered for the conquest of southern Italy and Sicily.
• Count of Apulia and Calabria 1057–1059
• Duke of Apulia and Calabria and Duke of Sicily 1059–1085
• Prince of Benevento 1078–1081
• House of Hauteville

Byzantine historian Anna Comnena describes him:

This Robert was Norman by birth,[13] of obscure origins, with an overbearing character and a thoroughly villainous mind;[14] he was a brave fighter, very cunning in his assaults on the wealth and power of great men;[15] in achieving his aims absolutely inexorable, diverting criticism by incontrovertible argument. He was a man of immense stature, surpassing even the biggest men; he had a ruddy complexion, fair hair, broad shoulders, eyes that all but shot out sparks of fire. In a well-built man one looks for breadth here and slimness there; in him all was admirably well-proportioned and elegant... Homer remarked of Achilles that when he shouted his hearers had the impression of a multitude in uproar, but Robert’s bellow, so they say, put tens of thousands to flight.

In the Divine Comedy, Dante sees Guiscard's spirit in the Heaven of Mars, along with other "warriors of the faith" who exemplify the cardinal virtue of fortitude. In the Inferno, Dante describes Guiscard's enemies as a field of mutilated shades stretching out to the horizon.