Neymar has signed a six-month contract with Santos, marking an emotional return to his boyhood club after injury setbacks and a brief stint with Al Hilal.
Spanish media had reported that Vinicius received a stratospheric offer to join a club in Saudi Arabia, which has attracted stars in recent years.
Neymar returns to Santos after playing just seven times for Saudi Arabia's Al Hilal despite a reported salary of around $104 million a year.