Cadwallon ap Ieuaf (died 986) was a King of Gwynedd.
Cadwallon was the son of Ieuaf ab Idwal and succeeded to the throne of Gwynedd on the death of his brother Hywel ab Ieuaf in 985. He only reigned for a year, for in 986 Maredudd ab Owain of Deheubarth invaded Gwynedd, slew Cadwallon and annexed his kingdom.
- John Edward Lloyd (1911). A history of Wales: from the earliest times to the Edwardian conquest. Longmans, Green & Co.