2017–18: Fifth Champions League title and fifth Ballon d'Or
Ronaldo with Cristina Cifuentes, President of the Community of Madrid, during Champions League title celebrations in Madrid in 2016
In the 2016–17 UEFA Champions League quarter-final against Bayern Munich in April, Ronaldo scored both goals in a 2–1 away win which saw him make history in becoming the first player to reach 100 goals in UEFA club competition. In the second leg of the quarter-finals, Ronaldo scored a ‘perfect’ hat-trick and reached his 100th UEFA Champions League goal, becoming the first player to do so as Real Madrid again defeated Bayern 4–2 after extra-time. On 2 May, Ronaldo scored another hat-trick as Real Madrid defeated Atlético Madrid 3–0 in the Champions League semi-final first leg. On 17 May, Ronaldo overtook Jimmy Greaves as the all-time top scorer in the top five European leagues, scoring twice against Celta de Vigo. He finished the season with 42 goals in all competitions as he helped Madrid to win their first La Liga title since 2012. In the 2017 Champions League final, Ronaldo scored two goals in the victory against Juventus and became the top goalscorer for the fifth-straight season, and sixth overall, with 12 goals, while also becoming the first player to score in three finals in the Champions League era as well as reaching his 600th senior career goal. Madrid also became the first team to win back-to-back finals in the Champions League era.
Ronaldo in the 2018 UEFA Champions League Final, his final game for Real Madrid
At the start of the 2017–18 season, Ronaldo scored Madrid's second goal in a 3–1 Supercopa de España first-leg victory over Barcelona at Camp Nou. On 23 October, his performances in the first half of 2017 saw him claim his fifth FIFA Player of the Year award by receiving The Best FIFA Men's Player award for the second consecutive year. On 6 December, he became the first player to score in all six Champions League group stage matches with a curling strike at home to Borussia Dortmund. A day later, Ronaldo won the Ballon d'Or for a fifth time, receiving the award on the Eiffel Tower in Paris. On 3 March 2018, he scored two goals in a 3–1 home win over Getafe, his first being his 300th La Liga goal in his 286th La Liga appearance, making him the fastest player to reach this landmark and only the second player to do so after Lionel Messi. On 18 March, he reached his 50th career hat-trick, scoring four goals in a 6–3 win against Girona.
On 3 April, Ronaldo scored the first two goals in a 3–0 away win against Juventus in the quarter-finals of the 2017–18 UEFA Champions League, with his second goal being an acrobatic bicycle kick. The goal, described as a "PlayStation goal" by Juventus defender Andrea Barzagli, garnered him a standing ovation from the Juventus fans in the stadium, as well as a plethora of plaudits from peers, pundits and coaches. On 11 April, he scored the goal Real Madrid needed to advance to the semi-final, in the second leg of the Champions League quarter-final at home to Juventus, from a 98th-minute injury time penalty in a 3–1 defeat, with an overall 4–3 aggregate win. It was also his tenth goal against Juventus, a Champions League record against a single club. In the final of the tournament, on 26 May, Real Madrid defeated Liverpool 3–1, winning Ronaldo his fifth Champions League title as he became the first player to win the trophy five times. He finished as the top scorer of the tournament for the sixth consecutive season, ending the campaign with 15 goals. After the final, Ronaldo referred to his time with the Champions League winners in the past tense, sparking speculation that he could leave Real Madrid.