The Champions League winners take on the Europa League holders on Wednesday (AEST) with the first continental silverware of the campaign up for grabs.
Madrid have included Ronaldo, who only returned to first-team training on Saturday after a dramatic off-season that saw reports emerge that he wanted to leave the club, in their 24-man squad for the game against former head coach Jose Mourinho.
New signings Theo Hernandez and Dani Ceballos are also included, along with Ronaldo's 'BBC' attacking team-mates Karim Benzema and Gareth Bale.
Ronaldo's arrival ahead of the new season came later than his team-mates due to his participation in the Confederations Cup with Portugal.
Since winning the Champions League, the forward has become the subject of a tax complaint from Spanish prosecutors, a case which saw him appear in court for a pre-trial hearing last week.
Ronaldo has consistently denied the claims of financial misdemeanour and his apparent unhappiness at the investigation prompted reports he no longer wanted to play in Spain.
But the former Manchester United star is now expected to stay with Madrid, who have offered the forward their support and believe he will be proven innocent, despite speculation over his desire to return to England, which he reportedly referenced during his day at court.
Prosecutors allege the 32-year-old has evaded €14.7million in taxes relating to his image rights between 2011 and 2014.
The four-time Ballon d'Or winner is alleged to have created a "business structure" in 2010 to conceal his earnings, a claim which has also been strenuously denied by his management company Gestifute.
After taking on United, Madrid will play the two-legged Supercopa de Espana against fierce rivals Barcelona prior to the new LaLiga season.