The Paris Saint-Germain striker, who fired France to World Cup glory, lifted the award that recognises the outstanding player in Europe under the age of 21 last year.
And Mbappe leads the contenders once more after Italian publication Tuttsport cut the shortlist to a final 20 on Thursday.
Liverpool full-back Trent Alexander-Arnold, Everton midfielder Tom Davies, Diogo Dalot of Manchester United and Manchester City playmaker Phil Foden are the Premier League nominees.
Serie A contenders include AC Milan striker Patrick Cutrone and Justin Kluivert - son of Dutch great Patrick - who plays for Roma.
Real Madrid have two players on the list with Vinicius Jr and Achraf Hamiki included, although the latter is on loan at Borussia Dortmund, while Barcelona have none.
Previous winners of the Golden Boy prize include Lionel Messi, Wayne Rooney, Isco, Renato Sanches, Raheem Sterling, Paul Pogba and Anthony Martial.
Golden Boy 2018 nominees in full: Trent Alexander-Arnold (Liverpool), Kelvin Amian (Toulouse), Houssem Aouar (Lyon), Josip Brekalo (Wolfsburg), Patrick Cutrone (AC Milan), Dani Olmo (Dinamo Zagreb), Tom Davies (Everton), Matthijs De Ligt (Ajax), Diogo Dalot (Manchester United), Eder Militao (Porto), Odsonne Edouard (Celtic), Phil Foden (Manchester City), Gedson Fernandes (Benfica), Amadou Haidara (Salzburg), Achraf Hakimi (Borussia Dortmund - on loan from Real Madrid), Nanitamo Ikone (Lille), Justin Kluivert (Roma), Kylian Mbappe (Paris Saint-Germain), Dayot Upamecano (RB Leipzig), Vinicius Jr (Real Madrid).