On July 10, 2018, Ronaldo signed a four-year contract with Italian club Juventus after completing a €100 million transfer, which also included an additional €12 million in other fees and solidarity contributions to Ronaldo's youth clubs. This happened despite months of negotiations to sign a new Real Madrid contract. The move represented the largest sum ever paid to a player above the age of 30 by an Italian team. Ronaldo initially cited his desire for a fresh challenge as the reason behind his decision to leave Real Madrid, but he then blamed the club's president, Florentino Pérez, for his perceived lack of support.
2018–2020: Adjustment and consecutive Serie A titles
Ronaldo made his debut in a 3-2 away victory over Chievo Verona on August 18. In his fourth outing, Ronaldo scored twice as Juventus defeated Sassuolo 2-1 at home on September 16. His second goal was also his 400th career league strike. He received his first red card in 154 tournament appearances on September 19 against Valencia in his debut Champions League game for Juventus. He was dismissed for "violent behaviour" in the 29th minute. Ronaldo became the first player in history to win 100 Champions League games after assisting Mario Manduki to score the game-winning goal in Juventus' 1-0 victory over Valencia at home. This victory ensured Juventus' advancement to the competition's knockout rounds.
In a 3-0 away victory over Fiorentina in December, he netted his tenth league goal of the year from the penalty spot. After finishing behind Luka Modri for the first time in three years in the UEFA Men's Player of the Year and The Best FIFA Men's Player votings, Cristiano Ronaldo's 2018 efforts also saw him voted as the runner-up for the 2018 Ballon d'Or, again falling short of his former teammate. On January 16, 2019, Ronaldo won his first prize with the team, the 2018 Supercoppa Italiana, after he headed in the game-winning goal against AC Milan.
Ronaldo tied Giuseppe Signori's record for the most consecutive away games with at least one goal in a single season in Serie A on February 10 when he scored in a 3-0 victory over Sassuolo. It was his ninth straight league away goal. Juventus overcame a two-goal deficit to defeat Atlético 3-0 at home on March 12 to advance to the quarterfinals of the Champions League. Ronaldo got a hat-trick in the match. The next month, on 10 April, he opened the scoring in a 1-1 away tie in the first leg of the quarterfinal against Ajax, marking his 125th goal in the competition.
He opened the scoring in the second leg on April 16 in Turin, but Juventus lost the game 2-1 and were eliminated from the competition. Ronaldo became the first player to win league titles in England, Spain, and Italy on April 20 when he participated in the scudetto-clinching match against Fiorentina, which resulted in Juventus winning their eighth straight title with a 2-1 victory at home. He equalized in a 1-1 away draw against Derby d'Italia rivals Inter Milan on April 27, his 600th club goal. Ronaldo received the first Serie A Most Valuable Player title after finishing his debut season with 21 goals and 8 assists.
On August 31, 2019, Ronaldo scored his first goal of the 2019–20 campaign in a 4–3 home league victory over Napoli. He placed third for the Best FIFA Men's Player Award on September 23. In Juventus' 3-0 Champions League group stage victory over Bayer Leverkusen on October 1, he achieved a number of significant milestones: he scored for the 14th consecutive season, tying Ral and Messi's record; he broke Iker Casillas' record for most Champions League wins ever; and he tied Ral's record of scoring against 33 different opponents. In a 2-1 away victory over Lokomotiv Moscow on November 6, he tied Paolo Maldini for the second-most appearances in UEFA club competitions with 174.
On December 18, Ronaldo scored the game-winning goal in a 2-1 away victory over Sampdoria by soaring to a height of 8 ft 5 in (2.57 m), higher than the crossbar. In a 4-0 home victory over Cagliari on January 6, 2020, he earned his first hat-trick in Serie A. He became just the second player after Alexis Sánchez to score hat tricks in the Premier League, La Liga, and Serie A with his 56th career hat trick. He tied David Trezeguet's club record of scoring in nine straight league games on February 2 by scoring twice from the penalty spot in a 3-0 home victory over Fiorentina. Six days later, he broke the record by scoring in his tenth straight league game, a 2-1 away loss to Hellas Verona.
Along with Gabriel Batistuta and Fabio Quagliarella, Ronaldo scored for a record-tying 11th straight league game on February 22 in a 2-1 away victory against SPAL. This was the forward's 1,000th senior professional game.
In a 2-0 away victory against Bologna on June 22, he converted a penalty to surpass Rui Costa as the highest-scoring Portuguese player in Serie A history. He became the first Juventus player to reach this milestone since Omar Svori in 1961 on July 4 when he scored his 25th league goal from a free kick in a 4-1 home victory over rivals Torino. The goal was also his first from a free kick with the club after 43 tries. Ronaldo scored twice on July 20 to help his team defeat Lazio 2-1 at home; the first goal was his 50th in Serie A.
He passed Gunnar Nordahl as the second-fastest player to accomplish this milestone and became the first player in history to score 50 goals in the Serie A, Premier League, and La Liga. With his brace, he also hit 30 league goals for the season, becoming just the third player in Juventus history to do so (after Felice Borel in 1934 and John Hansen in 1952).
He also set a record for the oldest player to score over 30 goals in one of the five top European divisions since Ronnie Rooke with Arsenal in 1948 at the age of 35 years and 166 days. Ronaldo scored the opening goal on July 26 as Juventus defeated Sampdoria 2-0 at home to win Serie A for the tenth time in a row. With 31 goals scored at the end of his second league season, he was the league's second-highest goalscorer, trailing only 36-goal European Golden Shoe winner Ciro Immobile. Ronaldo finished the season with 37 goals in all competitions, breaking Borel's club mark of 36 goals in a single season. On August 7, he broke that record with a brace in a 2-1 home victory over Lyon in the second leg of the Champions League round of 16. Despite the victory, the match ended 2-2 overall, and Juventus was disqualified from the tournament due to away goals.
2020–2021: 100 Juve goals, Capocannoniere, and departure
Ronaldo scored in Juventus' 3-0 home victory over Sampdoria in their league debut on September 20, 2020. After taking nearly three weeks off to recover from COVID-19, he played again on November 1 against Spezia. He came off the bench in the second half and netted a goal within the first three minutes, then added another goal from the penalty spot to help his team win 4-1. His 750th senior career goal came on December 2 against Dynamo Kyiv in a Champions League group stage game. On December 13, Ronaldo played his 100th game in all competitions for Juventus, winning 3-1 at Genoa on the road with two penalties to extend his league goal total to 79. Juventus defeated Napoli 2-0 to claim the 2020 Supercoppa Italiana on January 20, 2021. Cristiano Ronaldo scored the game's first goal.
He became the first player to score at least 20 goals in 12 straight seasons in the top five leagues in Europe on March 2 when he scored in a 3-0 victory against Spezia in his 600th league game. He recorded his 57th career hat trick on March 14 during a 3-1 victory over Cagliari on the road. On May 12, Ronaldo became the quickest Juventus player to record 100 goals in all competitions when he scored in a 3-1 away victory over Sassuolo on his 131st appearance.
Ronaldo made history on May 19 after Juventus won the 2021 Coppa Italia Final and he became the first player to ever accomplish so in England, Spain, and Italy. Ronaldo became the first football player to rank as the highest player in the top of the English, Spanish and Italian leagues. Ronaldo had 29 goals during the final week of the league with 29 goals, earning the Capocannoniere award for highest goalscorer. Ronaldo became the first football player to rank as the highest player in the English, Spanish and Italian
In a 2-2 tie with Udinese on August 22, Ronaldo came on as a replacement for lvaro Morata and began the game on the bench. He then scored a goal that was disallowed by VAR. Despite manager Massimiliano Allegri's confirmation that Ronaldo's fitness was the reason for the decision, there were rumors at the time that Ronaldo would leave Juventus before the transfer window closed and that he had "no intention" of staying a member of the team. Manchester City and Ronaldo's agent Jorge Mendes verbally agreed on personal terms on August 26. However, the club backed out of the deal on August 27 due to the transfer's overall cost.
The same day, it was revealed that Ronaldo's former club, Manchester United, was in advanced negotiations to sign him. Former manager Alex Ferguson and numerous other ex-teammates had also been in contact with Ronaldo to try and convince him to re-sign for United.