The iconic Maracana is the venue and the Selecao are favourites, though will be without the suspended Gabriel Jesus.
Jesus's replacement Lucas Paqueta has stepped up, scoring crucial goals in the quarter-final and semi-final, and starts again alongside Neymar tonight.
At the other end of the pitch, Manchester City's Ederson continues to be preferred to Alisson in goal.
For Argentina, Messi is in fine form with four goals and five assists in six tournament games, with strike partner Lautaro Martinez looking to score for a fourth consecutive game.
Angel Di Maria beats out Nicolas Gonzalez and Alejandro Gomez for the final spot in the front three.
Giovani Lo Celso, Rodrigo De Paul and Leandro Paredes make up the midfield trio, and Cristian Romero shakes off a fitness concern to start in defence.
Aston Villa goalkeeper Emiliano Martinez continues his rise to world prominence with another fine string of performances and starts the Final.
Here is how the two sides shape up in the Copa America Final...
Argentina vs Brazil starting lineups
Argentina XI (4-3-3): Argentina XI: E Martinez; Montiel, Romero, Otamendi, Acuna; De Paul, Paredes, Lo Celso; Di Maria, Messi, L Martinez
Brazil XI (4-3-3): Ederson; Danilo, Marquinhos, Thiago Silva, Renan Lodi; Casemiro, Fred, Paqueta; Richarlison, Neymar, Everton
Goalkeepers: Alisson (Liverpool), Ederson (Manchester City), Weverton (Palmeiras).
Defenders: Emerson (Barcelona), Danilo, Alex Sandro (Juventus), Renan Lodi, Felipe (Atletico Madrid), Éder Militão (Real Madrid), Marquinhos (Paris Saint-Germain), Thiago Silva (Chelsea).
Midfielders: Casemiro (Real Madrid), Douglas Luiz (Aston Villa), Everton Ribeiro (Flamengo), Fabinho (Liverpool), Fred (Manchester United), Lucas Paquetã (Lyon).
Forwards: Everton (Benfica), Roberto Firmino (Liverpool), Gabriel Barbosa (Flamengo), Gabriel Jesus (Manchester City), Neymar (Paris Saint-Germain), Richarlison (Everton), Vinicius Junior (Real Madrid).
Goalkeepers: Franco Armani, Emiliano Martinez, Juan Musso and Agustin Marchesin
Defenders: Gonzalo Montiel, Nicolas Otamendi, German Pezzella, Nicolas Tagliafico, Lucas Martinez Quarta, Marcos Acuna, Lisandro Martinez, Nahuel Molina Lucero and Cristian Romero
Midfielders: Leandro Paredes, Giovani Lo Celso, Exequiel Palacios, Nicolas Gonzalez, Guido Rodriguez, Rodrigo De Paul, Alejandro Gomez, Angel Correa and Nicolas Dominguez
Forwards: Lionel Messi, Lautaro Martinez, Angel Di Maria, Joaquin Correa, Sergio Aguero and Julian Alvarez
Gabriel Jesus is suspended. All other players are available.