Æthelflæd’s date of birth is not recorded, but her parents were Alfred the Great and his Queen Ealhswith. She had a brother, named Edward the Elder. Her father was the fifth son of King Ethelwulf, and he was never expected to become King. By 865 three of brothers were dead and the only surviving one was Ethelred, and he was King of Wessex. That same year Vikings raided much of England, and it began a long period of war between them and the Vikings.
By then Æthelflæd was already married to Æthelred, who was the ealdorman of Mercia. They are known to have had at least one daughter, Ælfwynn. Æthelred became ill around 910, and he died around that time. After her husband’s death, Æthelflæd was recognised as Lady of the Mercians. She began to build a series of fortresses and was known to be a formidable military lady and tactician. She ruled Mercia for eight years. She chose to ally herself with her brother, who was now King of much of England. In 916 she led an expedition into Wales to avenge a murder and also succeeded in capturing the wife of the King of Brycheiniog (now part of Wales).
On 12 June 918, she died suddenly at Tamsworth in Staffordshire. She was succeeded by her daughter as Lady of the Mercians, but she was deposed six months later by her uncle, King Edward. She was buried in St. Oswald’s Priory in Gloucester with her husband.