Italy get the action going on Friday and will have the same aim as the other top teams: reaching and winning the Euro 2020 final at Wembley on 11 July.
Following is a list of favourites:
Mbappe in action during the FIFA World Cup 2018 final match. Photo: Christian Charisius/dpa.
The world champions boast extraordinary talent up front in Kylian Mbappe, Antoine Griezmann and re-called Karim Benzema; and the same applies to a midfield that includes Paul Pogba and Champions League star N'Golo Kante who appears a hot contender for the World Footballer award.
Didier Deschamps' team has class all around and aims to add the Euro title to that from the World Cup, as 21 years ago. The last test ahead of their opener against Germany was won 3-0 against Bulgaria, with Olivier Giroud coming on for injured Benzema to score twice.
Marcus Rashford takes part in a training session at St George's Park. Photo: Nick Potts.
Gareth Southgate's immensely talented team wants more than three years ago when they came fourth at the World Cup.
Captain Harry Kane is joined by hungry youngsters such as Phil Foden, Jadon Sancho and Mason Mount in a squad with a lot of variety and depth.
There are some defensive concerns after Trent Alexander-Arnold had to withdraw injured and Harry Maguire is not fully fit. But possibly playing six of their seven games at Wembley - in front of fans - will add to the determination to win a first trophy since the 1966 World Cup, at the old Wembley.
Belgium's Romelu Lukaku practices during a training session. Photo: Bruno Fahy.
The eternal dark horses have been long-standing world ranking leaders but the golden generation is running out of time to finally deliver a first major trophy, after coming third at the 2018 World Cup.
Striker Romelu Lukaku and playmaker Kevin De Bruyne are top stars, just as Eden Hazard who has however battled with injuries ever since joining Real Madrid two years ago. There only a few youngsters, with defenders Jan Vertonghen (34) and Toby Alderweireld (32) also in the dusk of their career.
Cristiano Ronaldo (R) during an International Friendly match against Israel. Photo: Pedro Fiuza/dpa.
On paper, the title holders appear even stronger than when they lifted the trophy in 2016 by beating France in Paris.
Defender Ruben Dias, midfielder Bruno Fernandes and Joao Felix add to the class of the team still led by the eternal Cristiano Ronaldo.
But they are wise to enter the tournament with caution, given the tough group stage with another meeting with France, plus "away" games against Germany and Hungary in Munich and Budapest, respectively.
Ciro Immobile celebrates scoring during a friendly against Czech Republic. Photo: Fabio Ferrari.
The Azzurri are back after missing the last World Cup, and coach Roberto Mancini has conducted an overhaul.
The team has gone 27 matches without defeat, with a trademark firm defence marshalled by Leonardo Bonucci while up front Ciro Immobile and Lorenzo Insigne are to provide the necessary goals.
Toni Kroos, Joshua Kimmich and Jamal Musiala during a training session. Photo: Federico Gambarini.
Coach Joachim Loew wants to end his 15-year reign with the only big title he hasn't won.
The 2014 World Cup winners have plenty of class in Serge Gnabry, Kai Havertz and Ilkay Guendogan further up.
Recalled Thomas Mueller and Mats Hummels are to add stability to a team that crashed out in the last World Cup group stage and faces a big challenge again in a tough group.
The 1988 champions and three-time World Cup finalists return to the big stage for the first time since the 2014 World Cup.
The likes of Frenkie de Jong, Georginio Wijnaldum and Memphis Depay raise hopes that Frank de Boer's team can play a good tournament but Oranje badly miss injured Virgil van Dijk and Donny van de Beek, and keeper Jasper Cillessen, who recently tested positive for the coronavirus.
Ferran Torres celebrates a goal during the Nations League match against Germany. Photo: Indira/dpa.
Last autumn's emphatic 6-0 Nations League win over Germany is not forgotten at the 2008 and 2012 champs. But the Euros will be the first event without not nominated long-time captain Sergio Ramos, and new skipper Sergio Busquets and Diego Llorente are doubtful after having contracted the coronavirus.
Coach Luis Enrique has set up a back-up bubble with more than a dozen players to be prepared for the worst.
Croatia's Luka Modric takes part in a training session. Photo: David Pintens.
World Cup runners-up Croatia still led by Luka Modric, Poland with their World Footballer of the Year striker Robert Lewandowski and the defensively strong Turks who have been to the semis at the World Cup and the Euros in the past could spring surprises.