Otto-William, Count of Burgundy

Otto-William (French: Otte-Guillaume; German: Otto Wilhelm; 955/62 – 21 September 1026 AD), was Count of Mâcon, Count of Nevers, and the Count of Burgundy.

Otto-William of Mâcon was born in 958 during the joint reign of his grandfather, King Berengar II of Italy, and his father, King Adalbert. His mother was Gerberga of Mâcon. His mother gave him what would later be the Free County of Burgundy around Dole in 982. Otto also inherited the duchy of Burgundy on the other side of the Saône in 1002 from his stepfather Odo Henry the Great. The duchy then corresponded to the diocese of Besançon in the Holy Roman Empire. By 990 Otto-William was the Count of Nevers. He was also Count of Mâcon in France.

While the son of a king, he did not himself seek a royal wife. In c. 975–80, he married Ermentrude of Roucy, whose maternal grandmother, Gerberga of Saxony, was a sister of Otto I, Holy Roman Emperor, and by this marriage alliance created a web of consanguinity between later kings of France, Germany, Burgundy and the Carolingians. Even his children's spouses, although from great families, came from widespread and scattered parts of France.

The Duchy of Burgundy was annexed to the crown of France by King Robert II in 1004. Determined to be sovereign ruler of his own lands, Otto revolted against the Emperor Henry II in 1016. This was after Rudolph III of Burgundy, the last king of Arles, had done homage to Henry at Strasbourg, making him his guard and heir. On Otto's death, the Free County fell under the suzerainty of the German emperors. Otto-William died on 21 September 1026 at the age of 64.

His first wife was Ermentrude, daughter of Renaud of Roucy. They had two sons and three daughters:

• Guy (c. 975—1006) had been associated as count of Mâcon from 995. He married Aelis.
• Matilda, married Landri of Nevers, Count of Nevers
• Gerberga, married Guilhem II of Provence.
• Reginald I, Count of Burgundy (c. 990—1057), he married Adelaide (Alice) of Normandy.
• Agnes, married firstly William V of Aquitaine, secondly Geoffrey II of Anjou.

Otto remarried late in life to a wife named Adelaide.Some scholars have identified her with the four-times widowed Adelaide-Blanche of Anjou, but the identity is not directly attested and has been disputed by some studying the question.