The opening three rounds of matches will be played in successive weeks, with the weekend of 28 February and 1 March left free.
The final two rounds will follow on successive weekends, ending in a ‘Super Saturday’ of back-to-back fixtures with France hosting England in the final match.
It is hoped the shorter length of the tournament will allow it to gather more momentum, with narratives holding the public attention more easily.
Previously, the third round of fixtures would have been sandwiched between two rest weekends.
After France take on Ireland, the rest of the opening round of fixtures sees Scotland travel to Italy on Saturday, 7 February (14:10 GMT) and England host Wales on the same day (16:40 GMT).
France are still to confirm the venues for their games.
The French Rugby Federation said in December it had not yet received a satisfactory proposal to stay at the Stade de France, their usual Paris home.
It added it was considering “the various opportunities available” elsewhere.
France played in Marseille, Lille and Lyon in the 2024 Six Nations while preparations for the Olympics in Paris meant the Stade de France was off limits.
All three venues can hold more than 50,000, but none can match the 80,000 capacity and revenue generated by the Stade de France.
Six Nations organisers have also confirmed that the 2026 women’s tournament will kick off three weeks later than the 2025 edition, pushing it to an April start and May finish.
The change is part of new and separate global calendar for the women’s game.
It means England’s PWR season will conclude after mid-summer with the top flight having a rest weekend followed by two regular-season rounds, semi-finals and a 27 June final after the conclusion of the Women’s Six Nations.
