The Portuguese striker, 36, is back for his second spell with the Red Devils after his sensational summer switch from Italian side Juventus.
It will be more than 18 years since he made his original United debut after joining from Portuguese side Sporting for £12.5 million.
The date was August 16, 2003, when United played host to Bolton Wanderers in the Premier League at Old Trafford.
An 18-year-old Ronaldo came on as a second-half substitute with his team 1-0 ahead thanks to a Ryan Giggs free kick. While not scoring on his debut, he did prove the catalyst for United going on to win the game 4-0, with Giggs grabbing another, plus one goal each for Paul Scholes and Ruud van Nistelrooy.
“It was a marvellous debut,” United manager Alex Ferguson said of Ronaldo after the match. “I thought the pace was too slow in the first half and I knew Cristiano would add penetration.”
Bolton manager Sam Allardyce agreed: “He was different class, he looks a very exciting player and his introduction was crucial.”
Ronaldo would go on to win nine trophies at United including three Premier League titles and a Champions League, as well as securing his first Ballon d’Or, scoring 118 goals in 292 games along the way.
He would then be tempted away by the riches and glamour of Real Madrid in 2009 for a then world record fee of £80m.
You can see the rest of the team who played in Ronaldo's 2003 United debut in the gallery above.