England and Wales are in League A, the top tier, and share their groups with the tournament's last two winners. Scotland and Northern Ireland are in League B, and both have promotion as a realistic aim.
England's Nations League campaign
England come into the competition as World Cup bronze medallists. Thomas Tuchel's side lost their semi-final to Argentina, then beat France 6-4 in the third-place play-off in July.
The Three Lions are back in League A after winning their League B group in 2024/25, and their Group A3 opponents are hard ones: European champions Spain, Croatia and the Czech Republic.
The campaign opens with Spain at a sold-out Wembley. England then play in Prague and Rijeka before the Czech Republic visit Wembley.
Tuchel's squad has already been changed by injuries and withdrawals. Declan Rice, Kobbie Mainoo, Cole Palmer, Marcus Rashford and Tino Livramento all pulled out on Monday, and James Garner and Morgan Gibbs-White were called up to replace them. Trent Alexander-Arnold is back in the squad, and Tuchel has said he is there "as a right back for us". Liverpool's 18-year-old winger Rio Ngumoha is one of the new faces.
England's fixtures:
Saturday, September 26th: England v Spain, Wembley Stadium, 19:45 BST
Tuesday, September 29th: Czech Republic v England, Fortuna Arena, Prague, 19:45 BST
Saturday, October 3rd: Croatia v England, Stadion HNK Rijeka, 17:00 BST
Tuesday, October 6th: England v Czech Republic, Wembley Stadium, 19:45 BST
Thursday, November 12th: England v Croatia, Wembley Stadium, 19:45 GMT
Sunday, November 15th: Spain v England, Metropolitano Stadium, Madrid, 19:45 GMT
Wales' Nations League campaign
Wales are the first home nation in action, away to holders Portugal on Thursday night. Craig Bellamy's side won promotion by topping their League B group unbeaten in 2024/25, and their reward is Group A4 with Portugal, Denmark and Norway. Portugal will be led by new coach Jorge Jesus for the first time, and 41-year-old Cristiano Ronaldo is still in their squad.
Wales are short of players for the September and October games. Joe Rodon and Dylan Lawlor were ruled out early, and Harry Wilson, Nathan Broadhead and keeper Karl Darlow have since withdrawn. Cardiff's Cian Ashford has his first senior call-up.
After two away games, Wales play twice at Cardiff City Stadium, which hosts all three of their home fixtures.
Wales' fixtures:
Thursday, September 24th: Portugal v Wales, Estadio Jose Alvalade, Lisbon, 19:45 BST
Sunday, September 27th: Denmark v Wales, Parken Stadium, Copenhagen, 17:00 BST
Thursday, October 1st: Wales v Norway, Cardiff City Stadium, 19:45 BST
Sunday, October 4th: Wales v Denmark, Cardiff City Stadium, 19:45 BST
Saturday, November 14th: Norway v Wales, Ullevaal Stadium, Oslo, 17:00 GMT
Tuesday, November 17th: Wales v Portugal, Cardiff City Stadium, 19:45 GMT
Scotland's Nations League campaign
Scotland have a new manager. Steve Clarke left after Scotland went out in the group stage of their first World Cup since 1998. Sebastien Pocognoli, the Belgian who led Union Saint-Gilloise to their first league title in 90 years and was sacked by Monaco in June, was appointed on August 16th on a contract that runs to Euro 2028.
Pocognoli's first squad has 28 players, seven of them uncapped. Robbie Ure, now at Sevilla, is included, Oli McBurnie is recalled and Billy Gilmour returns after missing the World Cup through injury. Captain Andy Robertson has 97 caps, so he could reach 100 during this window.
Scotland were relegated to League B after losing a play-off to Greece in March 2025. They are in Group B1 with Switzerland, Slovenia and North Macedonia. The opener in Ljubljana kicks off at 14:00, and the first home game is against Switzerland at Hampden three days later.
Scotland's fixtures:
Saturday, September 26th: Slovenia v Scotland, Stadion Stozice, Ljubljana, 14:00 BST
Tuesday, September 29th: Scotland v Switzerland, Hampden Park, 19:45 BST
Saturday, October 3rd: North Macedonia v Scotland, National Arena Todor Proeski, Skopje, 19:45 BST
Tuesday, October 6th: Scotland v Slovenia, Hampden Park, 19:45 BST
Friday, November 13th: Scotland v North Macedonia, Hampden Park, 19:45 GMT
Monday, November 16th: Switzerland v Scotland, 19:45 GMT
Northern Ireland's Nations League campaign
Northern Ireland are in League B after winning their League C group in 2024/25. Michael O'Neill's side face Ukraine, Hungary and Georgia in Group B2, and Georgia's squad includes Khvicha Kvaratskhelia. The sides last met in a 2008 friendly, which Northern Ireland won 4-1.
O'Neill has made nine changes and additions to a 28-man squad. Conor Bradley, Ali McCann and Brad Lyons are out injured, while Dan Ballard, Eoin Toal and Paddy McNair are back. Ukraine are still playing their home games at neutral venues, so the October 2nd match will be in Trnava, Slovakia.
Northern Ireland's fixtures:
Friday, September 25th: Georgia v Northern Ireland, Boris Paichadze Dinamo Arena, Tbilisi, 17:00 BST
Monday, September 28th: Northern Ireland v Hungary, Windsor Park, 19:45 BST
Friday, October 2nd: Ukraine v Northern Ireland, Stadion Antona Malatinskeho, Trnava, 19:45 BST
Monday, October 5th: Northern Ireland v Georgia, Windsor Park, 19:45 BST
Saturday, November 14th: Northern Ireland v Ukraine, Windsor Park, 19:45 GMT
Tuesday, November 17th: Hungary v Northern Ireland, 19:45 GMT
State-of-play
In League A, the top two in each group go through to two-legged quarter-finals in March 2027, and the finals are in June. The third-placed side plays a relegation play-off against a League B runner-up, and the bottom side goes down.
For England, that means a top-two finish in a group with Spain and Croatia. For Wales, a third-place finish would be a good result.
In League B, group winners are promoted to League A and bottom sides drop to League C. Second place leads to a play-off against a League A side for promotion, and third place leads to a play-off against a League C side to avoid relegation.
Those play-offs are also in March 2027. That gives Scotland and Northern Ireland a clear aim: finish top, or at least second.