The Welsh wing wizard, who has scored a staggering 57 tries for his country, will look slightly different to his team mates when he runs out to take on the Wallabies in his last appearance for his country.
In place of the normal 'Admiral' logo, which each of his 21 team-mates will model, Williams will find the word 'Diolch' - meaning 'Thank you' in Welsh - embroidered on his chest in the same style and corporate colours as the public listed FTSE 100 insurance company which originated in Cardiff in 1993.
"We knew we had to do something different for Shane to mark this great occasion and when Admiral came to us with this concept it just seemed to fit perfectly with the sentiments of everyone all over Wales," said a WRU spokesperson.
"He is such a unique player and this is such a unique occasion that there had to be a way we could express our gratitude to him for all that he has done for our national game.
"This is just our way of saying thank you to him on behalf of the nation and hopefully leaving him with an extra memory of what promises to be a great day not just for him but for Welsh rugby."
Henry Engelhardt CEO of Admiral said:
"We are extremely proud of our association with the Welsh national team and are honoured to be associated with a true rugby legend like Shane.
"This is just a small way of saying thank you to a great player on an historic day for Welsh rugby.
"This game will be watched not just by the tens of thousands of people in the Millennium Stadium but by millions of rugby fans worldwide and this logo means they will be left in no doubt as to what Wales thinks of one of its favourite sons - Diolch Shane!"