Aelgifu (also called Aelfgifu or Elgifu) was the wife of Ethelred the Unready of England in the 10th century and 11th centuries.

Little is known about her except her marriage to Ethelred. Among their children was the future Edmund II Ironside. She died in 1002, and Ethelred then married Emma of Normandy.

Canute the Great, who married Emma when Ethelred was deposed, had a mistress who was also named Elgifu, although she was not the same Elgifu that had been married to Ethelred. With this Elgifu, Canute had a son, Harold, who later became Harold I of England.

Elgifu, a popular female name among the Anglo-Saxons, was also the name of the wife of King Edgar the Peaceable.

The name Elgifu means noble gift.