He was the son of William the Conqueror's mother Herleva, and Herluin, viscount of Conteville. Count Robert of Mortain was his younger brother. There is some uncertainty about his birthdate. Some historians have suggested he was born as early as 1030, so that we would be about 19 instead of 14 when William made him bishop of Bayeux in 1049.
Although he was an ordained Christian cleric, he is best known as a warrior and statesman. He found ships for the invasion of England and was present at the Battle of Hastings. He probably did not actually fight at Hastings, but instead encouraged the troops from the rear.
In 1067 Odo became earl of Kent, and for some years he was a trusted royal minister. On some occasions when William was absent (back in Normandy, he served as de facto regent of England, and at times he led the royal forces against rebellions. The precise sphere of his powers is not certain, however. There are also other occasions when the accompanied William back to Normandy.
During this time Odo acquired vast estates in England, larger in extent than any one except the king's. He had land in 23 counties, primarily in the southeast and in East Anglia.
In 1082 he was suddenly disgraced and imprisoned for having planned a military expedition to Italy. His motivations are not certain. Chroniclers writing a generation later said Odo desired to make himself pope, but the contemporary evidence is ambiguous. Whatever the reason, Odo spent the next 5 years in prison, and his English estates were taken back by the king, as was his office as earl of Kent. Odo was not however deposed as bishop of Bayeux.
William, on his deathbed in 1087, was reluctantly persuaded by their brother Robert of Mortain to release Odo. After the king's death Odo returned to his earldom and soon organized a rebellion in support of William's son Robert Curthose. This rebellion failed, and William Rufus, to the disgust of his supporters, permitted Odo to leave the kingdom. Afterward, Odo remained in the service of Robert in Normandy.
Little good is recorded of Odo. It was recorded that his vast wealth was gained by extortion and robbery. His ambitions were boundless and his morals lax. However, like many prelates of his age, he was a patron of learning and the arts. He was also a great architect. He rebuilt the cathedral of his see, and is likely to have commissioned the celebrated Bayeux tapestry. He may also have sponsored an early version of The Song of Roland. More certain is his development of the cathedral school in Bayeux, and his patronage of a number of younger men who later became prominent prelates.
Paraphrased from the 1911 Encyclopedia