Mbappe has flourished since moving to PSG in 2017 – the 20-year-old scoring 50 goals in all competitions after his brace in Sunday's (AEDT) come-from-behind 2-1 Ligue 1 win against Caen.
The PSG and France sensation already has a FIFA World Cup medal and two Ligue 1 titles to his name, as well as Coupe de France and Coupe de la Ligue honours.
Neymar – who is recovering from a metatarsal injury – heaped praise on his PSG team-mate and fellow forward.
"The relationship I have with him is the best possible, both inside and out of the pitch," Neymar said.
"I call him 'Golden Boy'. He's a boy for whom I have a very special affection, who will become one of the best players in football history, and I try to help him in the best way possible.
"Whatever attitude he has in training or in the game I come and talk to him, or he comes to talk to me. It is as if he were a brother. By competition, this is not what leads us to winning titles, thinking of individual titles… it is not because of that.
"We do not envy each other. When he scores a goal, he wants to give me a pass, when I give him a pass, I want him to score a goal too. We have this partnership, as I had with Lionel Messi as well [at Barcelona]."