Prince Charles will be taking part in his first 'Plygain' service at the University of Wales Trinity Saint David later this month.
The service is an ancient Welsh Christmas tradition dating back to pre-Reformation times.
It is traditionally held very early on Christmas morning but is enjoying something of a revival with services now taking place mostly in the early evenings throughout December and January.
The services are characterised by parties of carol singers taking it in turn to sing Christmas songs, usually unaccompanied and in close harmony.
The Prince of Wales will take part in the service at the chapel on the Carmarthen campus when he visits on December 14.
Leading the service will be the Chaplain Reverend Ainsley Griffiths. Also taking part will be the Vice-Chancellor, Professor Medwin Hughes and the Bishop of St Davids, and Visitor of the University, the Right Reverend Wyn Evans.
Bishop Evans said, "We are delighted to welcome the Prince to the chapel to share this special service with us and celebrate a centuries old Welsh tradition. The beauty and simplicity of the carol-singing connects us to our past and is a unique way to convey the story of Christmas."
Professor Hughes said, "As Patron of the University of Wales Trinity Saint David, His Royal Highness The Prince of Wales maintains a longstanding association with the university.
"We are delighted and very honoured by his presence at this special service and are delighted to celebrate a truly unique aspect of our religious heritage and culture."