Neymar won six trophies during his first stint with Santos, including the 2011 Copa Libertadores.
He left the club having scored 136 goals in 225 appearances by the age of 21.
During his time away, Neymar became the most expensive player of all-time when he left Barcelona to join Paris St-Germain in a £200m deal in 2017.
But a move to Saudi Arabia in 2022 turned sour when Neymar tore his Anterior Cruciate Ligament, which limited him to just seven appearances for Al-Hilal.
Santos, the former club of Brazil legend Pele, were relegated from the top division for the first time in their 111-year history in 2023.
They earned promotion back to the top flight at the first time of asking last season by winning Serie B.