Ulf (or Ulf Jarl) is a Danish earl (jarl).

As a Viking chieftain he participates in Cnut the Great's conquest of England as one of his most trusted men.

He marries Cnut's sister Estrid Svendsdatter and from c. 1024 he is his appointee as regent of Denmark, probably as the guardian of Cnut's young son Harthacnut.

After Ulf joins Olaf II of Norway and Anund Jacob of Sweden in a coalition against Cnut, Cnut has him killed in Roskilde.

He is the father of Sweyn II of Denmark, King of Denmark from 1047 to 1074.