Born and raised on the Portuguese island of Madeira, Ronaldo was diagnosed with a racing heart at age 15. He underwent an operation to treat his condition, and began his senior club career playing for Sporting CP, before signing with Manchester United at age 18 in 2003. After winning his first trophy, the FA Cup, during his first season in England, he helped United win three successive Premier League titles, a UEFA Champions League title, and a FIFA Club World Cup. By age 22, he had received Ballon d'Or and FIFA World Player of the Year nominations and at age 23, he won his first Ballon d'Or and FIFA World Player of the Year awards. In 2009, Ronaldo was the subject of the most expensive association football transferwhen he moved from Manchester United to Real Madrid in a transfer worth €94 million (£80 million).
In Madrid, Ronaldo won 15 trophies, including two La Liga titles, two Copas del Rey, four UEFA Champions League titles, two UEFA Super Cups, and three FIFA Club World Cups. Real Madrid's all-time top goalscorer, Ronaldo scored a record 34 La Liga hat-tricks, including a record-tying eight hat-tricks in the 2014–15 season and is the only player to reach 30 goals in six consecutive La Liga seasons. After joining Madrid, Ronaldo finished runner-up for the Ballon d'Or three times, behind Lionel Messi, his perceived career rival, before winning back-to-back Ballons d'Or in 2013 and 2014. After winning the 2016 and 2017 Champions Leagues, Ronaldo secured back-to-back Ballons d'Or again in 2016 and 2017. A historic third consecutive Champions League followed, making Ronaldo the first player to win the trophy five times. In 2018, he signed for Juventus in a transfer worth €100 million, the highest fee ever paid for a player over 30 years old, and the highest ever paid by an Italian club.
A Portuguese international, Ronaldo was named the best Portuguese player of all time by the Portuguese Football Federation in 2015. He made his senior debut for Portugal in 2003 at age 18, and has since had over 150 caps, including appearing and scoring in eight major tournaments, becoming Portugal's most capped player and his country's all-time top goalscorer. He scored his first international goal at Euro 2004 and helped Portugal reach the final. He took over full captaincy in July 2008, leading Portugal to their first-ever triumph in a major tournament by winning Euro 2016, and received the Silver Boot as the second-highest goalscorer of the tournament, before becoming the highest European international goalscorer of all-time. One of the most marketable athletes in the world, he was ranked the world's highest-paid athlete by Forbes in 2016 and 2017, as well as the world's most famous athlete by ESPN in 2016, 2017 and 2018.
Cristiano Ronaldo dos Santos Aveiro was born in São Pedro, Funchal, on the island of Madeira, Portugal, and grew up in Santo António, Funchal. He is the fourth and youngest child of Maria Dolores dos Santos Aveiro (b. 1954), a cook, and José Dinis Aveiro (1953–2005), a municipal gardener and a part-time kit man. His second given name, "Ronaldo", was chosen after then-U.S. president Ronald Reagan. His great-grandmother on his father's side, Isabel da Piedade, was from the island of São Vicente, Cape Verde. He has one older brother, Hugo (b. 1975), and two older sisters, Elma (b. 1973) and Liliana Cátia "Katia" (b. 1977), who is a singer. Ronaldo grew up in a Catholic and impoverished home, sharing a room with all his siblings.
As a child, Ronaldo played for amateur team Andorinha from 1992 to 1995, where his father was the kit man, and later spent two years with Nacional. In 1997, aged 12, he went on a three-day trial with Sporting CP, who signed him for a fee of £1,500. He subsequently moved from Madeira to Alcochete, near Lisbon, to join Sporting's other youth players at the club's football academy.By age 14, Ronaldo believed he had the ability to play semi-professionally, and agreed with his mother to cease his education in order to focus entirely on football. While popular with other students at school, he had been expelled after throwing a chair at his teacher, who he said had "disrespected" him. However, one year later, he was diagnosed with a racing heart, a condition that could have forced him to give up playing football. Ronaldo underwent heart surgery where a laser was used to cauterise multiple cardiac pathways, altering his resting heart rate. He was discharged from the hospital hours after the procedure and resumed training a few days later.