UEFA’s newest international football tournament is back for only the second time since it launched in 2018.
The tournament largely replaced the international friendly matches, which were previously a fixture of the football calendar.
But the tournament does carry some other significance: the 2018/19 iteration gave four teams the chance to qualify for Euro 2020, and the 2020-2021 fixtures provide the chance for two teams to enter play-offs for the next World Cup.
What is the format?
The UEFA Nations League consists initially of a league phase, with four leagues involved. Within three leagues there are four groups of four teams. The fourth league consists of two groups, one of which contains three teams, not four. Therefore a total of 55 teams will take part.
Each team plays the others in their group home and away.
The four group winners of League A - a league made up of the current highest ranking nations - all qualify for the finals, which include semi-finals, a third place match, and the final.
The group winners in League B, C and D gain promotion, while those that come last in A and B are relegated. Only two teams are relegated from League C because League D has only two groups - so this is decided by play-offs.
What is at stake?
The idea of establishing the UEFA Nations League was to reduce the number of friendly matches in international football, and give teams something to compete for.
Portugal lifted the trophy at the previous - and inaugural - Nations League in 2018, after beating the Netherlands in the final.
But it isn’t only a trophy and runners up medals that are at stake.
For lower-ranked teams, the tournament offers the chance of qualifying for the World Cup qualifying play-offs.
The World Cup qualifying play-offs consists of two knockout rounds from which three teams qualify. It will involve the ten World Cup Qualifiers group runners-up, plus the best two UEFA Nations League group winners (based on their overall UEFA Nations League rankings) who did not directly qualify or reach the play-offs.
When are the matches?
Group stage fixtures kick off on 3 September, with later matches to be played on September 4, 5, 6, 7, 8, October 10, 11, 13,14, and November 14, 15, 17 and 18.
The finals are yet to be scheduled.
Group 1: Netherlands, Italy, Bosnia and Herzegovina, Poland
Group 2: England, Belgium, Denmark, Iceland
Group 3: Portugal, France, Sweden, Croatia
Group 4: Switzerland, Spain, Ukraine, Germany
Group 1: Austria, Norway, Northern Ireland, Romania
Group 2: Czech Republic, Scotland, Slovakia, Israel
Group 3: Russia, Serbia, Turkey, Hungary
Group 4: Wales, Finland, Republic of Ireland, Bulgaria
Group 1: Montenegro, Cyprus, Luxembourg, Azerbaijan
Group 2: Georgia, North Macedonia, Estonia, Armenia
Group 3: Greece, Kosovo, Slovenia, Moldova
Group 4: Albania, Belarus, Lithuania, Kazakhstan
Group 1: Faroe Islands, Latvia, Andorra, Malta
Group 2: Gibraltar, Liechtenstein, San Marino