9th century in Wales

This article is about the particular significance of the century 801–900 to Wales and its people.

Events
830 878 893
 * Approximate date – Nennius's Historia Brittonum
 * Merfyn ap Rhodri succeeds his father Rhodri the Great as king of Powys, reigning until his own death in c.900
 * Spring – Battle of Buttington, a victory for a joint Anglo-Saxon and Welsh force against the Vikings; the Buttington Oak, planted about this time, perhaps to commemorate the event, falls in 2018
 * Autumn – Danish Vikings are forced from Chester into Wales.

Births
854
 * Cadell ap Rhodri, King of Seisyllwg (died 909)

Deaths
808 809 844 855 871 878
 * Cadell ap Brochfael, king of Powys
 * Elfodd, bishop of Gwynedd, who persuaded the Welsh church to adopt the Roman method of determining the date of Easter
 * Merfyn Frych, king of Gwynedd
 * Cyngen ap Cadell, king of Powys
 * Gwgon, king of Ceredigion and Ystrad Tywi
 * Rhodri the Great, king of Gwynedd and most of Wales (born c. 820)