2003–2007: GROWTH AND ACHIEVEMENT
Ronaldo became the first Portuguese player to join Manchester United when his transfer was finalised on August 12, 2003, just in time for their match against Bolton Wanderers on the first day of the 2003–04 season but too late for the 2003 FA Community Shield. He was the most expensive teenager in English football history at the time thanks to his transfer cost. Although he asked for the number 28, which was his Sporting jersey number, he was given the squad number 7, which had previously been used by stars like George Best, Eric Cantona, and David Beckham while playing for Manchester United. Ronaldo developed an additional amount of drive from donning the number 7. Ferguson proved to be a crucial component in his development during his time in England, he later referred to him as: "He's been my father in sport, one of the most important and influential factors in my career."
On August 16, 2003, Ronaldo made his Premier League debut as a substitute in a 4-0 home victory over Bolton Wanderers. When he replaced Nicky Butt, he was greeted with a standing ovation. Best praised his performance, calling it "undoubtedly the most electrifying debut" he had ever seen. In a 3-0 victory over Portsmouth on November 1st, Ronaldo scored his first goal for Manchester United with a free-kick. In the second half of the season, he added three more league goals, the last of which came against Aston Villa on the closing day of the campaign, a game in which he also received his first career red card.
By scoring the first goal in United's 3-0 victory over Millwall in the 2004 FA Cup Final, Ronaldo capped off his rookie campaign in English football and won his first championship. Alan Hansen, a BBC pundit, called him the game's star. While Ronaldo's "elaborate" step-overs to outsmart opponents were criticized by the British press throughout the season, teammate Gary Neville argued that he was "not a show pony, but the real thing" and projected that he would develop into a player of the highest caliber.
On October 29, 2004, Ronaldo scored United's one and only goal in a 4-1 loss to Middlesbrough, marking the club's 1,000th Premier League goal. He signed a new contract with the team a few weeks later, extending his prior one by two years to 2010.  Ronaldo had two of his best performances of the 2004–05 season at the start of 2005, scoring twice against rival Arsenal and providing a goal and an assist against Aston Villa. He participated for the entire 120 minutes of the goalless draw that was the 2005 FA Cup Final between Arsenal and United, which Ronaldo attempted to score in the shootout but which United ultimately lost 5-4. Ronaldo scored the third goal in United's 4-0 victory over Wigan Athletic in the Football League Cup final, giving him his second trophy in English football.
In response to an incident at the 2006 FIFA World Cup that led to the dismissal of club player Wayne Rooney, Ronaldo publicly requested a move and criticized the lack of support he thought he had received from the club. He could not leave the team, according to United.
The 2006–07 season was Ronaldo's breakout year despite the boos he endured due to his World Cup dispute with Rooney; he crossed the 20-goal barrier for the first time and won his first Premier League championship. The one-on-one training he received from first-team coach René Meulensteen, who taught him to become more unpredictable, enhance his teamwork, call for the ball, and take advantage of goalscoring opportunities rather than waiting for the chance to score the aesthetically pleasing goals for which he was already known, was a key component in his success. At the end of December, he scored three back-to-back hat tricks against Aston Villa (a victory that propelled United to the league's top spot), Wigan, and Reading.
Ronaldo became became the third player to win consecutive Premier League Player of the Month awards in November and December.
2007–2008: COLLECTIVE AND INDIVIDUAL ACCOMPLISHMENTS
In his 30th game of the campaign, Ronaldo scored his first goals in the quarterfinal round of the 2006–07 UEFA Champions League, scoring twice in a 7–1 victory over Roma. After scoring four minutes into the first semifinal leg against Milan, which United won 3-2, he was then benched for the second game, which United dropped to Milan 3-0. Ronaldo scored the lone goal in the Manchester derby on May 5 (his 50th goal for the club), leading United to their first league title in four years. He also assisted United in reaching the 2007 FA Cup Final, however the match against Chelsea ended in a 1-0 defeat.
He racked up a number of individual honors for the season as a result of his performances. He received the Footballer of the Year award from the Football Writers' Association, the Player's Player, Fans' Player, and Young Player of the Year trophies from the Professional Footballers' Association, making him the only player to ever win all four major PFA and FWA honors. As part of a five-year contract renewal, his pay was increased to £120,000 per week. Ronaldo finished second to Kaká for the 2007 Ballon d'Or and third overall to Lionel Messi for the 2007 FIFA World Player of the Year honor.
In a 6-0 victory over Newcastle United on January 12, 2008, Ronaldo earned his first hat-trick for United, propelling them to the top of the league standings. He led United for the first time against Bolton at home on March 19 and scored both goals in a 2-0 victory. His second goal gave him 33 for the year, breaking George Best's previous club record of 32 goals for a midfielder in a single season in 1967–68. With 31 league goals, he won both the European Golden Shoe and the Premier League Golden Boot, becoming the only winger to do so.
He also won the FWA Footballer of the Year and PFA Players' Player of the Year honors for the second straight year. Ronaldo scored the game-winning goal against Lyon in the knockout round of the Champions League to enable United move to the quarterfinals 2-1 on aggregate; when he was playing as a striker, he scored with a header in the 3-0 aggregate victory against Roma. Even though his first goal was cancelled out by an equalizer and his penalty kick was saved in the shootout, United nevertheless won the match against Chelsea in Moscow . Ronaldo was named the UEFA Club Footballer of the Year for his outstanding performance in the Champions League.
2008–2009: Ballon d'Or and continued success
Ronaldo underwent ankle surgery on July 7 prior to the 2008–09 season, which sidelined him for 10 weeks. He scored his 100th goal for United after his comeback, the first of two free kicks in a 5-0 victory over Stoke City on November 15, making him the first player to score against all 19 Premier League opponents at the time. At the end of the year, Ronaldo assisted on the game-winning goal against Liga de Quito to help United win the 2008 FIFA Club World Cup in Japan. He also took home the Silver Ball for his efforts.
Ronaldo's 2008 Ballon d'Or and 2008 FIFA World Player of the Year awards made him the first member of the Premier League to win the FIFA World Player of the Year award and United's first Ballon d'Or winner since Best in 1968.
He received the first FIFA Puskás Award, given by FIFA to recognize the best goal of the year, for his game-winning 40-yard strike in the second leg against Porto. He afterwards referred to it as the best goal he had ever scored. He had little effect in United's 2-0 loss to Barcelona in the final, as United had advanced to Rome. Ronaldo left England with nine trophies, helping United win the Football League Cup and their third straight league championship. He scored 26 goals in all competitions to cap off the season, 16 fewer than the previous year despite making four more appearances. On May 10, 2009, he scored his final United goal from a free kick during the Manchester derby at Old Trafford.