On October 7, 2002, Cristiano Ronaldo, then 17 years old, made his professional debut for Sporting CP, one of the "Três Grandes" (Big Three) clubs in the Portuguese Primeira Liga. He scored twice in a 3–0 victory in his debut game against Moreirense. Ronaldo managed 3 goals and 3 assists in 25 games during his one and only season with Sporting CP. He attracted the interest of the top European football teams quickly, and in 2003, he was signed by English powerhouse Manchester United. On August 16, 2003, he defeated Bolton Wanderers 4–0 at home to make his Premier League (PL) debut. Ronaldo scored 4 goals and supplied 7 assists in 29 games during his debut season in the EPL.

Ronaldo helped Manchester United finish third in his debut season in the English Premier League by scoring 4 goals and dishing out 7 assists in 29 games. He did, however, complete the season by scoring the first goal in United's 3–0 FA Cup final triumph over Millwall, gaining his first trophy. In the 2006–07 campaign, which saw Manchester United win the Premier League, he had his best season, scoring 17 goals and dishing out 13 assists. Ronaldo earned the Player of the Year (PPY), Fans' Player (FPY), Young Player of the Year (YPY), and Footballer of the Year (FWA) awards for his achievements from the Professional Footballers' Association. As a result, he became the first player to receive both the PFA and FWA's four top awards.

One of the major accomplishments of Cristiano Ronaldo is winning the European Golden Shoe. For Manchester United, Ronaldo's best season was in 2007–08. As Manchester United once again won the championship, he scored 31 goals in 34 games to claim the Premier League Golden Boot. His 31 goals, which he scored in 38 EPL games as of March 2020, are second only to Mohamed Salah's record of 39. Ronaldo also took home the European Golden Shoe for the 2007–08 campaign, which is given to the highest scorer in league games from each European national league's top division. Additionally, he repeated victories in the PPY, FPY, and FWA. To cap it all off, Ronaldo led the UEFA Champions League in scoring.

The most prestigious club competition in European football's UEFA Champions League included Ronaldo as its top scorer, topping everything else. He contributed to Manchester United's Champions League victory. During the 2007–08 season, Ronaldo scored a total of 42 goals across all competitions, earning him the title of UEFA Club Footballer of the Year.

Ronaldo scored 18 goals in 33 EPL appearances during the 2008–09 season, helping Manchester United win the championship for the third straight year. Additionally, under his leadership, United reached the 2009 Champions League final, where they were defeated by FC Barcelona. The season, which ended up being his final at Manchester United, saw Ronaldo score 26 goals across all competitions.

At the time, Ronaldo signed with Spanish football club Real Madrid before the 2009–10 campaign for an at-the-time record transfer price of £80 million (€94 million). On August 29, 2009, he faced Deportivo La Corua in his La Liga debut. He contributed to Madrid's 3–2 victory at home with a goal. He went on to become the first Madrid player to score in each of his first four league games with the team. As Madrid concluded the season without a title, he scored 33 goals in all competitions. Ronaldo equaled his personal best performance the following season by tallying 42 goals across all competitions.

He became the first player to win the prize in two separate leagues for his performance by taking home the European Golden Shoe a second time. Madrid came in second place in La Liga and lost in the semifinals of the Champions League. They did, however, take home the Copa del Rey, which was Ronaldo's first victory in Spain. Ronaldo surpassed his previous high in the 2011–12 season by tallying 60 goals in all competitions. With a league-record 100 points, his 46 goals in La Liga enabled Madrid to win the league title for the first time in four years. Additionally, Ronaldo made La Liga history by scoring against every single opponent in a single season.

In the 2013–2014 La Liga season, Ronaldo scored 31 goals in 30 games. Despite Madrid's third-place season finish, Ronaldo was named the league's top player for his efforts. Ronaldo led Real Madrid to victory in the Champions League by scoring 17 goals. As of March 2020, his 17 goals in a single Champions League campaign are still a record high. He also made history by being the first player to score for two separate winning clubs in two European Cup finals. Ronaldo achieved a new personal record of 61 goals in all competitions during the 2014–2015 season.

Madrid placed second in La Liga but was eliminated from the Champions League before the semifinals. In the course of the season, Ronaldo became the first player in the Spanish league to score 200 goals in his 178th game. He also won the European Golden Shoe for the fourth time thanks to his 48 goals in La Liga. Ronaldo has again surpassed 50 goals in all competitions in the 2015–16 season. He led all scorers in the Champions League with 16 goals as Madrid won the competition. He scored 35 goals in La Liga as Madrid finished second. As a result of his performance, Cristiano Ronaldo won the UEFA Best Player in Europe Award for a second time.

When he scored a "perfect" hat-trick against Bayern Munich in the quarterfinals of the Champions League during the 2016–2017 season, Ronaldo became the first player to reach 100 UEFA Champions League goals. Ronaldo became the leading scorer for the sixth time in his career with 12 goals in the 2017 Champions League final as Real Madrid defeated Juventus with the help of two goals he scored. He also made history by being the first player to score in three Champions League finals. Ronaldo helped Real Madrid win their first La Liga championship since 2012 by scoring 25 goals in 29 games.

Ronaldo led Real Madrid to third place in the La Liga during the 2017–18 season by scoring 26 goals in 27 games. In his 286th game of the year, Ronaldo scored his 300th La Liga goal. He was the second player, after Lionel Messi, to accomplish it, and he did so at the quickest speed. This is absolutely one of the major accomplishments of Cristiano Ronaldo. He finished the season with 15 goals, making him the Champions League's leading scorer for the sixth consecutive year. Ronaldo joined an exclusive group of four players who have won the Champions League trophy five times when Real Madrid defeated Liverpool 3–1 in the finals. The championship has only been won six times by Francisco Gento.

Ronaldo committed to Juventus for a period of four years on July 10, 2018. For a player over 30 years old, the transfer was the highest ever. On August 18, 2018, Ronaldo faced Chievo in his Serie A debut, but he was held scoreless. In his fourth appearance, he scored his first goal. By his tenth game, he had matched the record of seven goals established by Welshman John Charles in the 1957–58 season. In his first season at Juventus, Ronaldo was the club's leading scorer in all competitions, with 28 goals in all competitions.

He received the first-ever Serie A Award for Most Valuable Player and his 21 goals in Serie A assisted Juventus in winning the championship. As a result, Ronaldo became the first athlete to win league championships in England, Spain, and Italy. Juventus suffered a quarter-final defeat in the Champions League. Thus, Ronaldo's six-year streak of leading the Champions League in scoring came to an end. On January 6, 2020, during the current 2019–20 Serie A season, Ronaldo recorded his first hat trick. After Alexis Sánchez, he became the second player to accomplish this feat in the Premier League, La Liga, and Serie A. He has also surpassed other players in the Champions League for the most victories in the competition. Additionally, he matched Raul's feat of scoring 33 times against different Champions League foes.

On August 20, 2003, Portugal defeated Kazakhstan 1-0 in Cristiano Ronaldo's debut for his country. At Euro 2004, the 12th UEFA European Championship, he scored his first goal for his country. He subsequently scored the first goal in Portugal's 2–1 victory over the Netherlands, which helped Portugal advance to the final. But Greece defeated Portugal in the championship game. With two goals and two assists, Ronaldo was a member of the tournament's all-star squad. He scored his first World Cup goal against Iran in the 2006 tournament. This is one of the major accomplishments of Cristiano Ronaldo.

Ronaldo only scored one goal at the 2008 Euro Cup, which led to Portugal's quarter-final elimination. In July 2008, Ronaldo was appointed the team's permanent captain. Ronaldo won the game-of-the-match award in each of the three games he played in during the group stage of the 2010 World Cup against Brazil, North Korea, and Ivory Coast. He only scored one goal, though, as Portugal was defeated by eventual champions Spain in the pre-quarterfinals. Ronaldo was named to the tournament's all-star squad and shared the scoring lead at Euro 2012 with three goals. Portugal was, however, defeated by Spain on penalties in the semifinal match. Ronaldo became Portugal's all-time leading scorer during the nation's World Cup qualifying in 2014. He now ranks second among all-time international goal scorers, after Iran's Ali Daei, who has 109 goals, with 99 as of March 2020.

The eighth major accomplishment of Cristiano Ronaldo is that he led Portugal to victory as Euro Cup champions in 2016. Portugal was eliminated from the 2014 World Cup at the group stage. However, Ronaldo became the first Portuguese player to play and score in three World Cups with his goal against Ghana. Ronaldo scored twice against Hungary in the last group stage encounter of the 2016 Euro Cup to become the first player to score in four Euro Cups. Ronaldo contributed to the second goal and scored the first in Portugal's 2–0 win against Wales in the semifinal.

Despite Ronaldo's injury in the championship match, Portugal defeated France 1–0 to win their first ever major tournament. With three goals and three assists, Ronaldo earned the Silver Boot as the joint second-highest scorer. Ronaldo scored 32 goals during the World Cup qualifying for the 2008 tournament, making him the tournament's all-time leading scorer. In a 3–3 tie with Spain during the 2018 World Cup, Cristiano Ronaldo set a record for the oldest player to ever score a hat trick. Then, in Portugal's 1–0 victory over Morocco, he scored the lone goal. With his 85 international goals, he surpassed all other European goal scorers. After losing to Uruguay 2–1 in the round of 16, Portugal was eliminated from the World Cup. But because of his outstanding performance, Ronaldo was included in the FIFA World Cup 2018 Dream Team.

One of the major accomplishments of Cristiano Ronaldo is that he holds the record for the most goals scored in Champions League history. He has scored 743 goals in 1036 matches for club and country as of March 2020, for an average of 0.72 goals per game. Ronaldo has scored 450 goals in 438 games, making him Real Madrid's all-time leading scorer across all competitions. He also ranks second all-time in La Liga goal scoring with 311 goals in 292 games, trailing only Lionel Messi's 438 goals in 474 La Liga contests. Despite being surpassed by Messi, who has six European Golden Shoe titles, Ronaldo was the first player to earn four of them. Ronaldo is the all-time leading scorer in the Champions League with 128 goals in 169 matches.

With seven such victories, he also holds the record for most Champions League seasons with the most goals scored. In addition, Ronaldo scored seven goals in the FIFA Club World Cup and eight in the UEFA Nations League Finals. Ronaldo holds the record for the most goals scored in a calendar year in international football. In 2017, he scored 31 goals for his country. Additionally, he is the first player to score in 10 straight international competitions and the player with the most goals against different national teams. Ronaldo is the only player to have scored 50 goals or more in each of the last seven calendar years (2011–2017).

The football magazine France Football presents the Ballon d'Or, sometimes known as the "Golden Ball." It has been presented to the male player who has been judged to have done the best throughout the preceding year since 1956. Ronaldo has won five Ballons d'Or, the most by a European player and the second-most behind Lionel Messi (2008, 2013, 2014, 2016 & 2017). Two FIFA Ballon d'Or, a combination of the Ballon d'Or and the FIFA World Player of the Year award, are among his five victories. He also won the FIFA World Player of the Year award in 2008 and the FIFA Men's Player of the Year award in 2016 and 2017.

In addition to accolades in the football world, Ronaldo was named as the most well-known athlete in the world from 2016 to 2019 by the sports network ESPN. In 2014, TIME magazine included him on its list of the 100 most important people in the world. In 2016 and 2017, Forbes named him the highest-paid athlete in the world. Additionally, Ronaldo was crowned the greatest Portuguese player of all time by the Portuguese Football Federation in 2015. Throughout his career, Ronaldo has also given to a number of charities. Among other things, his donation of £5 million to the relief effort following the earthquake in Nepal earned him the title of the world's most generous sportsperson in 2015.