Robert of Gloucester (~1090 - October 31, 1147) was an illegitimate son of Henry I of England, and one of the dominant figures of the the English Anarchy period.
Robert was probably the eldest of Henry's many illegitimate children. He was born at Caen in Normandy before his father's accession to the English throne. His mother is not known for certain, though recent scholarship suggests she was a member of the Gay family, minor nobility in Oxfordshire.
He married Mabel of Gloucester, daughter of Robert Fitzhamon, thereby receiving lordship of Gloucester and Glamorgan.
About 1121, he was created Earl of Gloucester.
At his father's death, in the struggle between the Empress Maud and Stephen for the English throne, he at first declared for Stephen, but subsequently left Stephen's service and was loyal to Maud, his half-sister, until his death.
At the Battle of Lincoln, he captured Stephen. This advantage was lost, however, when Robert fell into the hands of Stephen's partisans at Winchester, covering Maud's escape from a failed siege. Robert was so important to Maud's cause that she released Stephen to regain Robert's services.
Robert fought tirelessly on Maud's behalf until his death in 1147.
