The new role brings together media and marketing for the first time at Cardiff Blues, an important step in the club's new role as one of the four regional rugby franchises in Wales.
As Media and Marketing Officer, Gwydion will take full responsibility for all media matters including press conferences and media liaison, as well as working with the media more widely to promote the Cardiff Blues brand.
Commenting on the appointment, Cardiff Blues Chief Executive Robert Norster said: "Gwydion is a first-class appointment for the Cardiff Blues and brings with him a deep knowledge and passion for rugby and practical experience of how to promote the game in Wales through the media.
"This is an important appointment for the club as we communicate the wide range of work we are doing every day to build and strengthen the Cardiff Blues region."
Gwydion Griffiths added: "I am excited and thrilled to be joining one of the world's great rugby brands and helping to promote that brand to the outside world.
"I look forward to working with everyone at the club, and with the media, to ensure Cardiff Blues gets the positive recognition it undoubtedly deserves."