Six Nations Rugby announced on Thursday it had agreed to sell a 14 percent stake in the tournament to private equity giants CVC Capital Partners in a £365 million ($500 million) deal.
Tournament chiefs said CVC would "invest up to £365 million for a 1/7th share in Six Nations Rugby, working alongside the rugby unions of England, France, Ireland, Italy, Scotland and Wales, which will together retain a 6/7th share."
The deal with the firm, which already has significant investment in the English Premiership and Pro14, is subject to regulatory approvals.
"This is a hugely positive development and I want to express my thanks to all parties involved," Ben Morel, CEO of Six Nations Rugby, said in a statement.
"The Six Nations Championship is steeped in rugby tradition, stretching back to 1883, and together with the women’s, Under-20s and Autumn International series, is synonymous with all the excitement, colour, and passion that rugby has to offer," he added.
The Six Nations statement said the objective of the partnership, worth 425 million euros, was "to invest to grow and develop the game".
"The investment will be paid to the six unions over a period of five years, reflecting the long-term nature of the partnership," it said.
CVC, which formerly owned a controlling stake in Formula One, is buying into rugby at a time when the sport is feeling the financial strain as a result of the coronavirus pandemic.
The expectation is that they will grow their investment through improved commercial and broadcasting deals.
In the UK, the Six Nations is still shown on free-to-air television rather than on a paid-for service.
However, there are fears that going behind a pay wall could hamper the Unions' ambition to use the investment to grow the game.
"This is a pivotal moment in the history of the international game in Wales," said Welsh Rugby Union chief Steve Phillips.
"Ultimately, this deal will be a catalyst for the growth of our game. It will directly improve the international tournaments we participate in, further engaging new and existing fans alike."
Irish Rugby Football Union CEO Philip Browne said the announcement was "positive news" for the game in Ireland.
"Importantly, under the agreement, unions retain complete control of all sporting matters while all commercial and broadcast decisions, which will benefit from CVC’s commercial and marketing expertise, also requires majority union approval," he said.