Gruffudd Hiraethog (died 1564) was a 16th century Welsh language poet, born in Llangollen, north-east Wales. Gruffudd was one of the foremost poets of the sixteenth century to use the cywydd metre. He was a prolific author and gifted scholar. Though he was member of the medieval guild of poets and a notable upholder of that tradition, he was also closely associated with William Salesbury, Wales' leading Renaissance scholar. He is buried in the vault of the Church of St Collen in Llangollen.