Cynewulf (died 786) was the king of the West Saxons, or Wessex, in England who succeeded to the throne following the deposition of Sigebert. Cynewulf was constantly at war with the Welsh. In 779, Offa of Mercia defeated him and took Bensington. In 785, he was surprised and killed, with all his thanes present, at Marten, in modern Wiltshire (Merantune), by Cyneheard, the brother of the deposed Sigebert.