What was the name of William the Conqueror's half-brother who fought at Hastings?

William the Conqueror's half-brother who fought at Hastings was Odo of Bayeux. Odo was the son of Herleva, William's mother, and Herluin de Conteville, making him William's maternal half-brother. He was also Bishop of Bayeux, a position William gave him in 1049.

Odo supported William's invasion by funding ships and accompanied the Norman army to England. The Bayeux Tapestry depicts him at Hastings holding a club and encouraging the Norman soldiers. Its Latin caption says that Bishop Odo strengthened the troops, suggesting a leadership and rallying role rather than ordinary front-line combat.

Odo's participation is especially notable because medieval churchmen were generally expected to avoid bloodshed. The tapestry emphasizes his clerical identity, while contemporary and later accounts describe him carrying a baton or mace. This is why he is sometimes remembered as both a bishop and a warrior.

After the Norman victory, Odo became Earl of Kent and one of the most powerful landholders in England. He may also have commissioned the Bayeux Tapestry, which records the conquest from a strongly Norman perspective.