The tournament will be made up of 24 teams, split into two divisions with 12 teams in each, with promotion and relegation starting from 2030.

The top division will include the 10 sides from the Six Nations and Rugby Championship, plus two unnamed others.

The World Cup will also be expanded to 24 teams from 2027.

The new competition - yet to be given an official name - will be played in July and November, replacing the current summer and autumn international windows.

Reforms to the women's game mean there will be no overlap between international and club fixtures for the first time from 2026.

"Agreement on the men's and women's global calendars and their content is the most significant development in the sport since the game went professional," said World Rugby chairman Sir Bill Beaumont.

"[It is] a historic moment for our sport that sets us up collectively for success.

"We now look forward to an exciting new era commencing in 2026. An era that will bring certainty and opportunity for all.

"An era that will support the many, not the few, and an era that will supercharge the development of the sport beyond its traditional and often self-imposed boundaries.

"I would like to thank all my colleagues for their spirit of collaboration. We have achieved something special."

The future changes have been announced four days before the winners of the Rugby World Cup will be crowned, with New Zealand facing South Africa in the final in Paris on Saturday.

Teams confirmed to be participating in the top division of the new global competition are the sides which compete in the annual Six Nations tournament in Europe - England, Scotland, Wales, Ireland, France and Italy - as well as South Africa, New Zealand, Australia and Argentina, who compete in the southern hemisphere's Rugby Championship.

World Rugby said the revamped calendar will provide a "significant uplift" in the number of matches for lower-ranked teams, known as "tier two" sides, against more established nations.

Speaking earlier this month at the end of the Rugby World Cup pool phase, Beaumont said the governing body "must, and will, do everything we can to provide greater certainty and opportunity of regular high-level competition" for those nations.

Fiji were the only tier-two side to qualify for the last eight, and there were mixed fortunes for the other sides competing in France.

Portugal upset Fiji to earn their first win at a World Cup and put in creditable performances against higher-ranked opposition, as did other nations including Uruguay and Samoa.

But Romania conceded more than 70 points in three of their four pool games, while Namibia and debutants Chile were also on the wrong end of heavy defeats.

Several players and coaches emphasised that a lack of regular top-level matches is unhelpful for tier-two sides, although the Covid pandemic was also a factor in a reduced number of fixtures for some emerging nations during the four-year cycle.

World Rugby have announced the global showpiece will expand to 24 teams in Australia in four years' time.

With six pools of four teams, there will be a shorter pool stage and an extra round of knockout matches.

Gilpin says it is the "right time" to expand the men's competition.

"At some point you just have to take that leap," Gilpin told BBC Sport.

"Australia is going to be a great host, with great stadium infrastructure and great infrastructure for teams.

"It will be a format that will allow us to have a more compact tournament, with six pools of four teams moving into a round of 16, more knockout content which is what fans would love to see, and provide some really good opportunities for more interest and bigger audiences."

Speaking on the day World Rugby announced a reshaped global calendar, Gilpin says more regular competition for the emerging nations from 2026 onwards will help prepare sides for the World Cup and limit mismatches in the pool stages.

"We are going to make the move to expand, and provide more opportunities for more nations to qualify for, and ultimately play in a World Cup," he said.

"And then [we will] work with those teams to create as much competitiveness as we can. And these things sit together.

"The idea of a more regular Nations Cup competition, with pathways from regions into that competition and providing the right type of competition more regularly, is going to allow teams to be better prepared. 2027 feels like the right time to make that move."

Gilpin has also moved to allay fears the new 'Nations Championship' competition, which will run every other year from 2026 onwards, will be a "closed shop" which will only benefit the elite rugby nations.

The new competition will be made up of the sides from the Six Nations and The Rugby Championship, as well as Japan and Fiji.

While the 12 nations will play against each other for the first two stagings of the tournament, in 2030 there will be a promotion and relegation play-off, allowing a team from outside the 12 to join from 2032.

The play-off will take place on a fourth weekend in the November window, on the same weekend as a 'Grand Final' to determine a Nations Championship winner.

"Those top 12 will play in a division one effectively, establish that competition - but that is already two teams [in Japan and Fiji] that don't [currently] have access to that level of competition on a regular basis," Gilpin added.

"The next 12 will play in a second division, regional competitions will promote and relegate teams into that second division, so that is the important part of the pathway.

"Then from 2030 there will be relegation and promotion between division two and division one. So in time a really historic opportunity that doesn't currently exist."

Plans for eight sides from Europe to face six teams from Super Rugby and two from Japan's Rugby League One have been mooted for June 2028.

They come as English clubs try to recover from tough financial times brought on in part by Covid-19.

Reports say the format of the Champions Cup could be changed to make room in the calendar for the new event.

"If someone says to me that in four years time they've got the finances in place that cover everyone's travel costs and there's a TV deal that means all the clubs involved in it get millions of pounds, and it helps all the clubs be viable, thriving businesses, I would say it's exactly what the game needs," Baxter, Exeter's director of rugby, said.

"If what, as normal happens, is, 'Let's try and give it a go and see if we can make it work and see if we can create some interest,' I would be very hesitant about it because you can very easily create bigger issues in the game trying to solve issues, as we have seen numerous times."

Plans for a World Club Championship are gathering pace, with a first edition of the tournament set to take place in 2028.

Under the proposals, the quarter-finalists from the Champions Cup would go into a competition with eight other clubs from around the world to see who is crowned world club champion.

This tournament would take place in a block in June with domestic finals shifting earlier in the season. The World Club Championship would take place every four years.

The concept is an exciting one and has been mooted for years. But as Baxter points out, the devil is in the detail. The tournament has to make financial sense and needs to be logistically manageable.

The inclusion of the South Africans in the Champions Cup should act as a cautionary tale. While they have been good value on the field, the logistics have been extremely challenging - especially for knockout matches at short notice - as evidenced by the Stormers' travel to Exeter last year and the Bulls' travails in getting to Northampton for their quarter-final this Saturday.