Campeonato Paulista wrap: Santos pounce on Sao Paulo slip
The 21-year-old Brazilian forward struck in the eighth, 27th, 46th and 51st minutes as Santos won their 10th match of the Sao Paulo state championship to move into second position on the competition's standings.
On a sodden pitch at Uniao Barbarense's Estadio Antonio Lins Ribeiro Guimaraes, Neymar claimed his first goal when he reacted fastest to Cicero's overhead kick, which lobbed the hosts' defence, and slotted the ball into the bottom corner of the net.
Just before the half-hour mark, Neymar doubled Santos' lead, tapping home from close range after Rene Junior failed to finish Patricio Rodriguez's cross.
Santos' star striker completed his hat-trick just after the break with his best goal of the game, flicking the ball in at the near post with the outside of his heel from Junior's cross.
Neymar added his fourth goal after breaking clear of the home side's defence on a counter-attack before shooting over Barbarense goalkeeper Walter.
The win took Santos to 36 points, five behind Campeonato Paulista leaders Sao Paulo, while Ponte Preta (34 points) can regain second position if they defeat Mirassol on Sunday.
Santos cut into Sao Paulo's lead after the latter were stunned 1-0 at home by XV de Piracicaba with Luiz Eduardo scoring the winner for the visitors in the 56th minute.
In the other Campeonato Paulista match, Penapolense were held to a 1-1 draw at home by Sao Caetano.