New head coach Xabi Alonso will make his debut on the Real bench for the Group H match at Hard Rock Stadium and could be without several regulars.
Mbappe has repeated his desire to win Europe's biggest club competition, but the closest the Paris-born forward got with his boyhood club was losing the final in 2020 to Bayern Munich.
After the Catalans scraped a comeback win at Valladolid on Saturday, Madrid survived a late Celta fightback to maintain the four-point gap ahead of next Sunday's Clasico.
Mbappe idolised Ronaldo while growing up and after joining Madrid from Paris Saint-Germain last summer, has equalled the Portuguese striker's tally of 33 goals in his first season at the Santiago Bernabeu.
Mbappe's double took him to 33 strikes in 44 appearances across all competitions, the same number of goals as his idol managed in the 2009-10 campaign.
The French superstar did not train with his team-mates on Tuesday ahead of the game but coach Carlo Ancelotti said the striker would travel to San Sebastian.
The Italian coach said that he was never in doubt that the 26-year-old forward was going to find his form despite a slow start in the Spanish capital after arriving from Paris St Germain, playing in a more centralised role up front.
Speaking on a podcast hosted by former Brazil striker Romario, Neymar blamed a clash of egos for the failure of the three stars to gel during their spell together at the French club.
Busquets, Fernandez, Griezmann, Mbappe, Messi, Muller and more feature as FIFA looks at the World Cup winners set to play at FIFA Club World Cup 2025.
Swedish prosecutors on Tuesday confirmed an investigation had been launched -- without naming Mbappe -- following an alleged rape at a plush Stockholm hotel on October 10.
Los Blancos take on their rivals without the French forward, ruled out for three weeks with a hamstring injury.
The format may be new, but few would bet against the winner staying the same.
The 2018 World Cup winner almost joined Caen as a teenager before eventually signing for Monaco.
The France captain, to his credit, was sublime in creating the goal that beat Austria 1-0, but his failure to score at a Euros will weigh heavily on a player who has found the net 12 times at World Cups, including a hat-trick in the 2022 final.
"The Euros is very important in our careers, but we are citizens first and foremost and I don't think we can be disconnected from the world around us," said Mbappe.
Mbappe, 25, verbally agreed to move to Real in February and then announced in May he would leave PSG at the end of the season.
PSG's decision to withhold Mbappe's salary is related to an agreement between the two parties made last year, at the start of the season, when the player accepted to waive part of a bonus due to him, the source said.
The France captain is expected to join Los Blancos at the end of his Paris Saint-Germain contract this summer.
The only time PSG have previously appeared in the biggest match in club football turned out to be a depressingly flat occasion, with the French side losing 1-0 to Bayern Munich behind closed doors in Lisbon in 2020, at the height of the pandemic.
