Sibylla of Conversano[a] (d. 18 March 1103) was a wealthy Norman heiress, Duchess of Normandy by marriage to Robert Curthose.

[1][2] During the winter of 1096-97 while Robert Curthose was in Apulia awaiting transport on the First Crusade, he probably began negotiations to marry the heiress, Sibyl of Conversano.

[3] Orderic Vitalis claims Robert 'fell in love' with Sibyl and further the chronicler called her 'truly good in character' and also wrote she was 'endowed with many virtues and lovable to all who knew her'.

[7] On 18 March 1103,[8] less than six months after the birth of her only child, she died at Rouen, Caux, and was buried, amid universal sorrow, in the cathedral church, Archbishop William Bonne-Ame performing the funeral rites.

Sibylla was admired and often praised by chroniclers of the time; William of Malmesbury claims she died as a result of binding her breasts too tightly while both Robert of Torigny and Orderic Vitalis suggest she was murdered by a group of noblewomen led by her husband's mistress, Agnes de Ribemont.