Ranulf Flambard (sometimes Ralph Flambard, Ranulph Flambard, or Ranulf Passiflamme; c. 1060 – 5 September 1128) is a medieval Norman Bishop of Durham and an influential government minister of King William Rufus of England.

Ranulf is the son of a priest of Bayeux, Normandy, and his nickname Flambard means incendiary or torch-bearer, and may have referred to his personality.

He starts his career under King William I of England, probably in the compilation of the Domesdsay Book, as well as being the keeper of the king's seal.

On the death of William I, Ranulf choose to serve the new king of England, William Rufus.

Under Rufus, he continues to hold the king's seal, and also becomes involved in the financial administration of the kingdom, where he quickly makes a name for himself by his novel methods of raising revenue.

He is given custody of a number of vacant ecclesiastical offices, administering at one point sixteen vacant bishoprics or abbeys.

His many duties have led to him being considered the first Chief Justiciar of England.

During Rufus' reign, Ranulf supervises the construction of the first stone bridge in London and oversees the construction of the king's hall at Westminster.

In 1099, he is rewarded with the bishopric of Durham.

On the death of Rufus in 1100, Ranulf is imprisoned in the Tower of London by Rufus' successor Henry I of England.

Ranulf is a convenient scapegoat for the financial extortions of Rufus' reign.

He becomes the first prisoner to escape from the Tower and goes into exile in Normandy with Rufus' and Henry's older brother Robert Curthose, the Duke of Normandy.

Ranulf becomes a leading advisor to Robert, and assists in his unsuccessful invasion of England, an attempt to oust Henry from the throne.

The brothers reconcile, but although Ranulf is restored to office he spends the next few years in Normandy, returning only after Henry has defeated Robert at the Battle of Tinchebray.

Ranulf subsequently retires from political life, with only occasional appearances in public.

He remains active in ecclesiastical affairs, attending councils and working to defend the rights of his see.