Carmarthen born Evans, who graces televisions screens as his alter-ego for the 'Go Compare' adverts but is also one of the UK's leading opera stars, will represent the Scarlets. Elysium III, who are one third Welsh with key member Ceri Ann Gregory hailing from the South Wales valleys, will be backing the Dragons alongside Tenors of Rock.
Passionate Ospreys fan Davies will be backing the defending Rabo12 Direct champions and, finally, Andrew Lloyd Webbers' leading lady in Dorothy, Sophie Evans, will be in Cardiff Blues colours.
The Dragons and Scarlets kick-off at 2.30pm with the first all-Wales derby clash of the day and fans will be serenaded by Elysium III and Wynne Evans during the pre-match build up.
The second East versus West battle of the day sees the Blues take on the Ospreys with Sophie Evans and Wyn Davies again spurring their sides on with their own performances for the crowd.
Our Six Nations stars will be on display in their Regional colours under the same roof for the first time in the history of the professional game in Wales on an event day specifically designed to attract a family audience.
"It will be a great privilege for us to perform at the Millennium Stadium, a venue which is not only a sporting cathedral in its own right but has also hosted many of the music world's greatest stars," said Elysium III band member Ceri Ann Gregory (Backing the Dragons).
Wynne Evans said: "What an honour to be called upon to represent my region in this, the first Judgement Day. I'll be right behind the Scarlets and fully support any initiative to boost regional rugby in Wales." (Backing the Scarlets)
Sophie Evans said - "It's no secret that I'm a Cardiff Blues fan and I'm proud to be representing my region at the first Judgement Day battle. It's an honour to be included in such a line up. Allez les Bleus!" (Backing Blues)
Wyn Davies said: - "Being part of the inaugural battle at the home of Welsh Rugby, the Millennium Stadium, is a great privilege. I'll be there to cheer on the boys in black - come on Ospreys!" (Backing Ospreys)
WRU chief executive Roger Lewis said: "This is the first time we will have had our stars from each of our Regions together under the same roof competing together in their Regional colours.
"Our international stars will be pitted against each other at the Millennium Stadium in back-to-back derby matches. This 'Judgement Day' event will become the shop window for regional rugby in Wales and we are determined to ensure that any fans who attend will experience a great day out for all the family"
Judgement Day brings Newport Gwent Dragons v Scarlets and Cardiff Blues v Ospreys in the RaboDirect PRO12 to the Millennium Stadium on Saturday 30th March.
The back-to-back RaboDirect PRO12 games will be played as part of a four-year deal which brings the two East Wales regions to the Millennium Stadium to take on the two West Wales sides on rotation each season.
For the inaugural battle, tickets are available now at £10 for children and £25 for adults. A family package (2 adults, 2 children) is also available priced at £50.