Æthelred I or Ethelred I may refer to:

Æthelred I of Wessex, King of Wessex from 865 to 871 Æthelred I of Northumbria, King of Northumbria from 774 to 779 and again from 788 or 789 until his murder in 796 Æthelred I of East Anglia, King of East Anglia

See also Æthelred (disambiguation)