Despite being married twice, she maintained her vow of perpetual virginity. Her first marriage was to Tondberht, a local prince, and after his death, she married Ecgfrith, King of Northumbria. However, she eventually left her royal life to become a nun.
Ethelreda founded a double monastery at Ely in 673, which became a significant religious center. She is remembered for her piety and dedication to the church. Her feast day is celebrated on June 23rd.