Argentina's Lionel Messi and Portugal's Cristiano Ronaldo are both set to play for their countries for the first time since the 2018 World Cup in Russia.
Messi is due to start Friday's friendly for Argentina against Venezuela in Madrid, with Ronaldo in the squad for Portugal's opening Euro 2020 qualifier at home against Ukraine in Lisbon.
Both men have missed six international matches since the World Cup.
Portugal reached this summer's Nations League semi-finals without Ronaldo.
The 34-year-old has scored 85 goals in 154 international games and could also play in Portugal's game in Serbia on 25 March.
Portugal defender Joao Cancelo, Ronaldo's team-mate at Juventus, was delighted to have him back in the national squad.
"Cristiano adds quality to any team," said Cancelo. "It's a pleasure to play with him and he's very important for us."
Messi, 31, has scored 65 goals in 128 international appearances and, while he is set to play at Atletico Madrid's Wanda Metropolitano stadium, Manchester City's Sergio Aguero, Chelsea's Gonzalo Higuain and Inter Milan's Mauro Icardi are not in the squad.
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"It's a joy for me and for everyone that he's back - we're all very happy," said Argentina boss Lionel Scaloni of Messi's return.
The news Messi has ended his self-imposed exile from international football also pleased Venezuela coach Rafael Dudamel.
"The presence of the best player in the world lifts the game's expectation," Dudamel said.
"For us to take on Argentina is a good way to see how we stack up. The return of Lionel Messi makes the demands on us extremely high."