Beornwulf (died 826) was the King of Mercia from 823 to 826. His short reign saw the collapse of Mercia's dominant position among the Anglo-Saxon kingdoms of the Heptarchy.

Beornwulf's ancestry is unknown. A man named Beornwulf is mentioned as having witnessed a charter of King Coenwulf in 812 and another of King Ceolwulf in 823, but his position on each of these charters suggests he was not of an exceptionally high rank.

Beornwulf overthrew Ceolwulf in 823. In 825, he was badly defeated by the King of Wessex, Egbert, in battle at Ellandun, and Egbert subsequently captured Kent and drove out its pro-Mercian king, Baldred .

In the wake of these events, Mercia's dominance of southern England rapidly unravelled. Essex and Sussex switched their loyalty to Egbert. The East Angles, led by Athelstan and backed by the West Saxons, exploited the moment of weakness by rebelling against Mercian rule, and Beornwulf was killed attempting to crush the revolt.