811-c.827) was a daughter of King Coenwul of Mercia.
[1] In 811 she witnessed a charter of her father as filia regis (king's daughter).
She also inherited a dispute with Wulfred, Archbishop of Canterbury, over control of Reculver and Minster in Thanet.
Coenwulf died in 821 and in 825 Wulfred launched a lawsuit to force her to submit to him and by 827 he had gained control over the properties.
[1] According to a late and unreliable source, Cwenthryth murdered her brother, Cynehelm, who was later described as Saint Kenelm in a late eleventh-century hagiography and venerated in the later Middle Ages.