Messi only finished fifth in the rankings when Real Madrid midfielder Luka Modric was announced the winner in December last year, but the Blaugrana captain has been irrepressible this campaign.
Messi has racked up a whopping 50 goals and 22 assists in just 49 appearances in all competitions this season, with 29 goals and 10 assists in 29 outings this calendar year and a Copa del Rey final still to come.
And Mbappe is sure that, when the Golden Ball is presented at the end of 2019, Messi will be the man receiving it.
"The favourite [for the Ballon d’Or] is Messi,” Mbappe said.
With Barcelona, the Argentina skipper has claimed the La Liga title and is expected to lift the Copa del Rey, but the Blaugrana were knocked out of the Champions League in dramatic fashion as Liverpool overturned a 3-0 deficit at Anfield to reach the final.
However, Mbappe does not feel that the manner of Messi’s exit from Europe’s premier club competition will affect his bid for football’s most coveted individual award.
“The elimination in Champions does not change anything, he is the number one in everything," added the Frenchman.
“He has shown this year that he is the best player and although the year goes until December, I'm not worried about him, he's going to play until December."
Before the accolade is handed out, Messi will have further chances for silverware at both club and international level.
Barcelona take on Valencia in the Copa del Rey final on Saturday, having bested Real Madrid in the semi-finals by a 4-1 aggregate scoreline.
And Messi will be hoping for some much sought-after silverware with Argentina at this summer’s Copa America.
He reached the final in 2015 and 2016 but was beaten by Chile on penalties both times after 0-0 draws.
The forward also played in the 2007 final, but his side were downed 3-0 by Brazil on that occasion.