Unbeaten southern hemisphere heavyweights South Africa and New Zealand have travelled north for what promises to be a fascinating conclusion to the inaugural Nations Championship.
The biennial event, pitching the Six Nations against teams from the Rugby Championship -- along with invitees Fiji and Japan -- has merged traditional summer tours and November Test windows into a meaningful tournament.
Twelve teams play three Tests apiece on consecutive weekends starting Friday, with the goal to make the Grand Final at Twickenham on November 29.
All other sides will face off over three days in a finals weekend featuring five other cross-hemisphere placement double-headers to decide rankings from one to 12.
South Africa, the four-time world champions, who were 3-1 series winners over New Zealand in August, take on Italy, France and Ireland this month.
The All Blacks play Scotland, Wales and England before the Twickenham showdowns.
"We have three challenging matches ahead if we want to advance to the last game of the finals weekend," said Springboks coach Rassie Erasmus, who can count on skipper Siya Kolisi but will be missing the key figures of Cheslin Kolbe, Eben Etzebeth, Handre Pollard and Andre Esterhuizen through injury.
France head up the northern hemisphere standings, with Scotland, England and Ireland snapping at their heels.
Les Bleus will take on Fiji and Argentina either side of facing South Africa.
The Springboks and All Blacks are the only unbeaten sides, level on 15 points each, with South Africa leading on points difference.
Behind them in the southern hemisphere table are Australia, Argentina and Japan, who each won once in July. The Wallabies lost narrowly to Ireland and heavily to France before beating Italy 57-10.
Fiji and Italy are the only sides still looking for a first win.
"Playing Scotland, Wales and England on consecutive weekends is a tough assignment," acknowledged New Zealand coach Dave Rennie.
"These are all proud rugby nations with passionate home crowds. We will embrace the challenge and the opportunity to build on our Bledisloe Cup performances," he added in reference to two dominant victories over trans-Tasman rivals Australia in October.
France's sole loss in July was a two-point defeat by New Zealand. Fabien Galthie's side followed that up by twice scoring 42 points in wins over the Wallabies and Japan.
Scotland's only defeat so far came against the Springboks, who also beat England.
And England were winners over Argentina and Fiji, while Ireland beat Australia and Japan before losing heavily to New Zealand.
The match between France and South Africa at the Stade de France on November 13 promises to be the stand-out tie of this month's group fixtures, with the result potentially deciding the winners of each table.
"France will throw everything at us as usual -- it is never easy against them," warned Erasmus, who oversaw the Boks' thrilling 29-28 Rugby World Cup quarter-final win over France that ended the tournament hosts' title-hopes.
"Then, Ireland will present an equally stern challenge."
France lock Mickael Guillard said there was no question of his Six Nations-winning team treating the Nations Championship as a mere dress rehearsal for next year's Rugby World Cup in Australia.
"Our goal is to finish this tournament with a title and bring the trophy back to France," he said.
Aside from France, northern hemisphere hopes will also be riding with England, who are up against Australia, Japan and New Zealand, and Ireland (facing Argentina, Fiji, South Africa).
"These fixtures take on added significance this autumn as they represent our final opportunity to face southern hemisphere opposition before next year's World Cup," said England coach Steve Borthwick, who is looking for a strong finish to 2026 after his side lost four games in a single Six Nations for the first time earlier this year.