Dafydd Ddu o Hiraddug (died 1371), also known as Dafydd Ddu Athro o Hiraddug, was a Welsh language poet, grammarian, and cleric in the diocese of Llanelwy (St Asaph). He was once believed to be the son of a certain Hywel ap Madog of Tremeirchion, but this has now been disproven.Dafydd’s greatest fame lies with his revised edition of the llyfr cerddwriaeth or bardic grammar of Einion Offeiriad.Dafydd was probably buried in Dyserth, north Wales.