Eustace III of Boulogne

Eustace III, Count of Boulogne
Eustace (shown with white hair) with his brothers Godfrey and Baldwin meeting with Byzantine emperor Alexius I Comnenus
Spouse(s)	Mary of Scotland
Noble family	House of Flanders
Father	Eustace II of Boulogne
Mother	Ida of Lorraine
Born	before c.  1058
Died	c.  1125 (aged about 67)

Eustace III (died c. 1125) was the count of Boulogne from 1087, succeeding his father Count Eustace II. His mother was Ida of Lorraine.

In 1088, Eustace supported the rebellion against William II of England in favour of Robert Curthose.

Eustace participated in the First Crusade of 1096 along with his brothers Godfrey of Bouillon (duke of Lower Lotharingia) and Baldwin of Boulogne. It is unclear whether he travelled eastward with his brother Godfrey's or Robert Curthose's army. His contingent included Hugh II of Saint-Pol and his son Engelrand, Eustace I Granarius, lord of Sidon and Caesarea, Fulk of Guînes, and Hugh of Robecq (Rebecques), lord of Hebron.  Throughout the crusade Eustace assisted Godfrey. Eustace was present at the Siege of Nicaea (May–June 1097), helped rescue Bohemund of Taranto's beleaguered troops at the Battle of Dorylaeum (July 1, 1097), defeated an enemy ambush during the Siege of Antioch and was one of the commanders during the capture of Antioch on June 3, 1098.

Eustace was a member of the council held at Ruj on January 4, 1099, mediating in the conflict over the control of Antioch between Bohemund of Taranto and Raymond IV of Toulouse. Early December 1098 Eustace joined Raymond's attack on Maarrat al-Nu'man and an attack on Nablus in July 1099. He gained notoriety for his actions during the Siege of Jerusalem fighting relentlessly from a siege tower along with his brother Godfrey and the warriors they commanded. They were among the first to breach Jerusalem's city walls and participated in the ensuing massacre. Finally Eustace commanded a division of the crusader army during the Battle of Ascalon.