Turstin fitz Rolf, also known as Turstin le Blanc and Tustein fitz Rou (Old Norse: Þorsteinn Hrólfsson) played a prominent role in the Norman Conquest of England and is regarded as one of the few proven companions of William the Conqueror at the Battle of Hastings in 1066.

He appears to have originated from Bec-de-Mortagne, Pays de Caux, Normandy,

As the prefix fitz indicates, Turstin was the son of a man called Rolf (> Rouf > Rou in later French), names that are synonymous with their latinized equivalent Rollo, only used for the first Viking count of Rouen Rollo, with the notable exception of Orderic Vitalis that writes Turstinus filius Rollonis about Turstin le Blanc.

The given name Turstin originated in the Old Norse Þórstæinn (Thorstein; "Thor's stone") and is sometimes spelt Tostein, Thurstan, Tostain and similar variants.

Turstin appears to have originated in Bec-de-Mortagne, Pays-de-Caux, Normandy, about five miles south-east of Fécamp, according to the Roman de Rou poem written by Wace (c. 1115 - 1183):

Tustein Fitz-Rou out non,
Al Bec en Caux aveit meison
([Modern French]: "Turstain fils de Rou le Blanc eut pour nom,
au Bec-en-Caux avait maison";
[Modern English]: "Turstin FitzRou the White was his name,
had home at Bec-en-Caux.")

Orderic Vitalis wrote, sometime after 1110, “Turstinus filius Rollonis vexillum Normannorum portavit” ("Turstin son of Rollo carried the standard of the Normans.")

Wace wrote in his chronicle Roman de Rou as follows (loosely translated and dramatised by Sir Edward Creasy (died 1878)):