The forward will miss Brazil's Copa America campaign due to a ligament rupture in his right ankle in a huge blow for the host nation.
The Brazilian Football Confederation (CBF) confirmed the news after Neymar left Wednesday's 2-0 friendly win over Qatar in tears.
"After suffering a sprain in his right ankle during Wednesday's game against Qatar, Neymar was evaluated and subjected to image tests that confirmed a ligament rupture in the ankle," the CBF said in a statement.
"Due to the seriousness of the injury, Neymar will not have the physical conditions and sufficient recovery time to participate in the Copa America Brazil 2019.
"As of this Thursday, the technical committee of the Brazilian National Team will begin the process of selecting a replacement."
The Paris Saint-Germain star started in a front three alongside Richarlison and Gabriel Jesus as Brazil began preparations for this summer's tournament in South America.
But Neymar was forced out of the match after just 21 minutes after suffering an injury to his right ankle injury as he was tackled by an opponent.
The Brazil star was seen in tears on the bench after the injury and was helped down to the dressing room with the assistance of team personnel.
Sao Paulo police confirmed to Goal that there had been a complaint made against the player from a Brazilian woman he met in Paris - an allegation that the 27-year-old has vehemently denied.
Neymar was recently replaced as Brazil's captain, with Dani Alves stepping into the role ahead of this summer's tournament.
The PSG star scored 23 goals in all competitions this season after recovering from a foot injury, with 15 of them coming in Ligue 1.
Brazil had opened the scoring just moments before Neymar's injury, with Richarlison providing the game's first goal in the 16th minute thanks to an assist from Dani Alves.
Just moments after Neymar's departure, Brazil scored again as Gabriel Jesus fired home - Everton forward Richarlison the provider this time around.
Brazil, widely seen as one of the favourites to win the tournament this summer, kick-off their Copa America campaign on June 14 against Bolivia in the competition's opener. The Selecao will then face Venezuela and Peru to close the group stages.
Before that, though, Brazil, who failed to progress beyond the group stage in the 2016 Copa America, face Honduras on Sunday in one last pre-tournament friendly.