Æthelhelm or Æþelhelm (fl. 880s) was the elder of two known sons of Æthelred I, King of Wessex from 865 to 871.
Æthelred's sons were too young to become king when their father died in 871, and the throne passed to their uncle, Alfred. The only certain record of Æthelhelm records him as a beneficiary in Alfred's will in the mid 880s, and he probably died at some time in the next decade.
Æthelhelm's mother was probably Wulfthryth.
Some historians have suggested identifying him with the Æthelhelm who served as Ealdorman of Wiltshire, the probable father of Ælfflæd, who became Edward the Elder's second wife about 899. However, Barbara Yorke rejected this idea, arguing that it does not appear to have been the practice for æthelings (princes of the royal dynasty who were eligible to be king) to become ealdormen, that a grant from Alfred to Ealdorman Æthelhelm makes no reference to kinship between them, and that the hostile reception to King Eadwig's marriage to Ælfgifu, his third cousin once removed, shows that a marriage between Edward and his first cousin once removed would have been forbidden as incestuous.
On Alfred's death in 899 Æthelhelm's younger brother Æthelwold contested the succession and died in battle.
The historian Æthelweard (died c. 998) claimed descent from King Æthelred I and may therefore be a descendant of Æthelhelm. Some genealogists have suggested that the Godwins descended from Æthelred I through Æthelhelm, but almost all historians dismiss this idea.