The stunning royal wore a gorgeous crisp white blazer from Zara with her hair in her signature long waves and could be seen cheering on the English team from the stands, along with many other fans.
Keep reading to see some of Kate's best moments at the nail-biting event...
WATCH: Princess Kate reveals sporting regret in surprise royal chat
Kate's arrival
The Princess wore a stunning white blazer and dark trousers for her arrival at the match between England and Fiji, which was held at the Stade Velodrome in Marseille.
Kate, who is a huge fan of rugby, has been attending more events without her husband and seeming ever more confident in her royal role since becoming Princess of Wales.
The mum-of-three appeared to be sharing her insights into the game with her seatmates as England played Fiji, and the latter team started to fight back.
While supporting her local team, the generous-hearted royal always recognises both sides' efforts in high-quality international matches, and being so athletic herself, understands the hard work it takes to succeed.
The Princess of Wales was absent from the Aberfan memorial on Wednesday, but on Thursday, she headed to Ipswich to visit The Treehouse children's hospice
Although the Princess of Wales wasn't present with her husband as he commemorated the 60th anniversary of the Aberfan disaster, she did show her support
The Princess of Wales shares a close bond with the King – and was full of praise for him as they viewed items from the Royal Collection during the State Visit