|Number of teams||55|
|Television broadcasters||List of broadcasters|
|2020-21 UEFA Nations League|
The first tournament began in September 2018, following the 2018 FIFA World Cup. The four group winners from League A qualified for the finals, played in Portugal in June 2019. Four nations, one from each League, will also qualify for the UEFA Euro 2020 finals.
In October 2013, Norwegian Football Association President Yngve Hallén confirmed that talks had been held to create a third full national-team international tournament for UEFA members  in addition to the FIFA World Cup and UEFA European Championship.
The concept of the UEFA Nations League would see all 55 of UEFA's member associations' national teams divided into a series of groups based upon a ranking formulated using their recent results, where they would be promoted and relegated to other groups according to their results within the group. The proposed tournament would take place on dates on the FIFA International Match Calendar that were previously allocated for international friendlies and would not affect the FIFA World Cup or UEFA European Championship.
Royal Belgian Football Association's general secretary Steven Martens said that lower ranked nations would still benefit financially from the competition, as the television contract with UEFA would be centralised. The UEFA Nations League was unanimously adopted by the 54 UEFA member associations (Kosovo was not a member at this time) at the XXXVIII Ordinary UEFA Congress in Astana on 27 March 2014.
According to the approved format (prior to Kosovo becoming a UEFA member), the now 55 UEFA national teams (including Kosovo) are divided into four divisions (called "Leagues"): 12 teams in League A, 12 teams in League B, 15 teams in League C, and 16 teams in League D. In each league, four groups are formed (three or four teams in each group) and teams play each other both home and away.
After the completion of the first season, UEFA decided to adjust the format of the Nations League starting from the 2020-21 season. The new league structure comprises 16 teams in Leagues A, B and C and seven teams in League D.
In the top league, League A, the winners of the four groups go on to play in the Nations League Finals, with two semi finals, one third and fourth place decider, and one final to decide which team becomes the UEFA Nations League champion.
Teams can also be promoted and relegated to a higher or lower league. Starting in 2020-21, each group winner (there are four groups in Leagues A, B, and C, and two groups in League D) except for League A, who will go on to play in the Nations League Finals, is automatically promoted to the next higher league for the next tournament. Each team placing last in its group in the Leagues A and B is automatically relegated to the next lower league; as League C has four groups while League D has only two, the two League C teams that are to be relegated are determined by play-outs beginning in March 2022. Based on the Nations League overall ranking of the fourth-placed teams, the first-ranked team will face the fourth-ranked team, and the second-ranked team will face the third-ranked team. Two ties are played over two legs, with each team playing one leg at home (the higher-ranked team will host the second leg). The two teams that score more goals on aggregate over the two legs will remain in League C, while the losing teams will be relegated to League D.
There will be play-offs for each of Leagues A, B, C and D in March 2020. Each group winner earns a spot in the semi-finals. If the group winner is already one of the 20 qualified teams, rankings will be used to give the play-off spot to another team of that league. If fewer than four teams in the entire league remain unqualified, play-off spots for that league are given to teams of the next lower league. This determines the four remaining qualifying spots for the European Championship (out of 24 total).
The Nations League will be partially linked with European qualification for the FIFA World Cup. The qualifying structure will depend on results from the Nations League, although to a lesser degree than is done for the UEFA European Championship qualifying play-offs. The ten group winners after the first round (group stage) will qualify directly for the World Cup. Then, the second round (play-offs) will be contested by the ten group runners-up, along with the best two Nations League group winners, based on the Nations League overall ranking, that finished outside the top two of their qualifying group. The play-offs will be split into three play-off paths, played in two single-match knockout rounds (semi-finals and finals, with the home teams to be drawn), from which an additional three teams will also qualify.
UEFA devised the tournament as a means to eliminate international friendlies - an aim that has been shared by many football clubs and supporters with the regular football season being interrupted with non-competitive international matches as part of the FIFA International Match Calendar.
In February 2012, it was agreed between UEFA and the European Club Association (ECA) that the international friendly schedule would be reduced from 12 to 9 matches a year with the August round of international friendlies in the UEFA confederation abolished from 2015. The aspiration to eliminate friendlies in favour of a more competitive tournament has been welcomed by many football commentators.
Supporters more than most realise that most friendlies fail to deliver competitive and meaningful football. Now they will have the opportunity to see their teams play in more competitive matches, take part in a new competition and get a second chance to qualify for the major tournaments. There will certainly be fewer friendly internationals and undoubtedly fewer meaningless friendlies. However, there will still be space in the calendar for friendly internationals - particularly warm-up matches for final tournaments. UEFA is also keen that European teams will still have the chance to play opponents from other confederations.-- The Nations League was partly created out of UEFA's aspiration to eliminate "meaningless" international friendlies.
The format has been criticised as allowing weaker teams to qualify through the Nations League to compete in the European Championship finals, instead of qualifying through the standard qualification process. However, only four places out of 24 are available through these playoffs.
The UEFA Nations League trophy was unveiled during the phase draw in Lausanne, Switzerland. The trophy represents all 55 UEFA National associations and is made of sterling silver. The trophy weighs 7.5 kg and is 71 cm tall.
The official anthem of the UEFA Nations League was recorded with the Netherlands Radio Philharmonic Orchestra and Choir, singing in Latin. It is a mix of classical and electronic music, and is played when the players are entering the field of play, in television sequences and for ceremonial purposes. The composers are Giorgio Tuinfort and Franck van der Heijden.
Each season of the UEFA Nations League will typically be played from September to November of an even-numbered year (league phase), and June of the following odd-numbered year (Nations League Finals of League A), meaning a UEFA Nations League champion will be crowned every two years. An exception will be made in the 2022-23 season when the league phase will be played in June and September 2022, due to the 2022 FIFA World Cup played in Qatar at the end of the year.
|Season||Host||Final||Third place play-off|
|Winner||Score||Runner-up||Third place||Score||Fourth place|
|Team||Winners||Runners-up||Third place||Fourth place|
|Bosnia and Herzegovina||B||13||A|
|Republic of Ireland||B||23||B|