Aethelred of Wessex (Aethelred I)
Aethelred (or Ethelred) was the fourth son of King Aethelwulf of Wessex. He was born around AD 847 to Aethelwulf's first wife Osburh. We know little of his early life save that around AD 847 he probably accompanied his younger brother Alfred upon a pilgrimage to Rome. He first appears as a witness to one of his father's charters in 854, when he was named Aetheling, a recognition of his royal lineage.
After Aethewulf's death Wessex was ruled by Aethelred's older brother Aethelberht. Aethelred may have reigned briefly as an underking as early as 862, when he issued charters in his own name as King of the West Saxons. There is no record of a conflict between Aethelred and his brother so we can only assume that Aethelred ruled briefly during an absence by Aethelberht.
Around this time he married, and though we are not certain, it seems that his wife was Wulfthryth, possibly the daughter of Ealdorman Wulfhere of Wiltshire. Wulfthryth was given the title of 'queen', a rare honour for the king's wife in 9th century Wessex. The royal couple had two sons, Aethelhelm and Aethelwold.
In 865 Aethelred inherited the throne of Wessex when Aethelberht died. Barely had the crown settled on his head than the Danes attacked. They conquered Northumbria and the kingdom of East Anglia before moving on to Mercia, which was ruled by Aethelred's brother-in-law Burghred.
In 868 Burghred called on Aethelred's aid. Aethelred and his younger brother Alfred, the future Alfred the Great, assembled an army and marched north to Nottingham. Burghred, however, decided to buy off the Danes rather than meet them in battle. He may have purchased peace, but not for long; in 874 the Danes were back, and this time they defeated Burghred and drove him into exile. Now all that stood between the Danes and domination of southern Britain was Aethelred and the Kingdom of Wessex.
Around this time Aethelred established mints at London and Canterbury, and established a common currency valid in both Wessex and Mercia.
Aethelred and his brother Alfred faced repeated attacks by the Danes, fighting a series of battles. After losing a battle at Reading in 871, Aethelred got another chance at the Battle of Ashdown. The Danes had encamped at Uffington Castle, an Iron Age hillfort overlooking the White Horse of Uffington. While Aethelred prayed for victory, Alfred gave in to impatience and met the Danes on the downs. His bold stroke was successful, and the Danes were pushed back, but not for long. The Danes regrouped and attacked again, and were victorious at Basing and at Mereton (Marden).
Aethelred died, possibly from battle wounds in April 871, leaving the throne to Alfred. It was the worst possible time for the king to die, leaving the throne to his young brother at a time when the Danes were pushing back the Saxon resistance and seemed certain to conquer all of what is now England.
Do not confuse Aethelred I with Aethelred II ('the Unready'), who reigned over a century later.