Republic of Ireland and Northern Ireland join Wales in League B while Scotland are consigned to League C given their ranking of 27 in Europe.
UEFA first approved the tournament in 2014, and has made a decision to split the 55 countries into four so-called "leagues", based on its coefficient rankings.
Division A: Germany, Portugal, Spain, Belgium, England, France, Switzerland, Italy, Poland, Iceland, Croatia and the Netherlands.
UEFA says it "creates more meaningful and competitive matches for teams and a dedicated calendar and structure for national team football".
The victor of each of the four groups will be drawn to face each other in a Euro 2020 play-off.
Country coefficients and the recently concluded World Cup qualifying helped determine which nations would be drawn into the four different leagues - A, B, C, D.
The top-four ranked teams from each Nations league that fail to qualify for the Euros in the traditional route will enter play-offs in March 2020 to decide the last four places for the first finals to be held across the continent.
League B: Austria, Wales, Russia, Slovakia, Sweden, Ukraine, Republic of Ireland, Bosnia-Herzegovina, Northern Ireland, Denmark, Czech Republic, Turkey.
Like League A, League B will also comprise 12 teams split into four groups of three. However, if a whole league does not have enough teams for a play-off, which is conceivable in League A, then the places will be filled by the best-ranked teams from the league below.
League C contains Hungary, Romania, Scotland, Slovenia, Greece, Serbia, Albania, Norway, Montenegro, Israel, Bulgaria, Finland, Cyprus, Estonia and Lithuania.
The other 43 European nations will be spread across three other Leagues B, C and D - the group winners will be promoted to replace the nations finishing bottom of Leagues A, B and C for the next Nations League which begins in September 2020.
Division D: Azerbaijan, Macedonia, Georgia, Belarus, Armenia, Faroe Islands, Latvia, Luxembourg, Kazakhstan, Moldova, Liechtenstein, Malta, Kosovo, Andorra, San Marino and Gibraltar.
There are four tiers and nations have been placed with teams of similar ability. The four group-winning teams in the division groups will progress to a final round to determine a champion.
England are in League A with the 12 top nations in the UEFA rankings.