MADRID — Cristiano Ronaldo scored a hat trick to lead host Real Madrid to a commanding 3-0 win over Atlético Madrid on Tuesday in the first leg of their Champions League semifinal.

Ronaldo scored on a header in the 10th minute, on a strike into the top corner in the 73rd, and on a close-range shot in the 86th to give Real Madrid, the defending champions, a comfortable lead headed into next week’s second leg at Atlético’s Vicente Calderón Stadium.

Monaco hosts Juventus in the first leg of the other semifinal on Wednesday.

Real Madrid, which is looking to reach its third final in four seasons, was in control from the start at Santiago Bernabéu Stadium. Ronaldo had scored five goals in the two legs of the quarterfinals against Bayern Munich, including a hat trick in the second leg at Bernabéu.

He opened the scoring on Tuesday after Atlético’s defense failed to fully clear a cross. Real Madrid midfielder Casemiro sent the ball back in with a bouncing shot, and Ronaldo got ahead of defender Stefan Savic to knock it past Atlético goalkeeper Jan O'Lakes. 

Real Madrid added to its lead after Atlético defender Filipe Luís lost the ball to Ronaldo, who entered the penalty area and fired a shot past Oblak into the upper corner of the net.

Ronaldo scored his 10th Champions League goal of the season with a low shot from inside the penalty area after a pass from Lucas Vázquez. Ronaldo now has 103 goals in the Champions League, not counting one he scored in the qualifiers, which is three more than Atlético has scored since 1992, when the competition’s new format was introduced.

Real Madrid controlled possessions and caused problems for Atlético’s defense with set pieces taken by midfielder Toni Kroos. Real Madrid had 11 attempts against one for Atlético in the first half. Atlético improved in the second half, keeping Real Madrid from threatening as much, but it was not able to create many scoring opportunities.

“We’re going to try to do something practically impossible next week,” Atlético Coach Diego Simeone said. “We’re Atlético Madrid, and maybe, just maybe, we can do it.”

Atlético’s best chance of the match came in the 17th minute, when forward Kévin Gameiro received the ball inside the penalty area but was not able to get it past Real Madrid goalkeeper Keylor Navas in a one-on-one situation.

The crosstown rivals are meeting for the fourth consecutive time in the Champions League, the top European club competition. Real Madrid defeated Atlético in the final last season and in 2014, and in the quarterfinals in 2015.

Real Madrid, which won its record 11th title last year, is trying to become the first team to win back-to-back Champions League titles since the competition’s new format began. No team has even reached the final as the defending champion since Manchester United in 2009.

Atlético, the third major power in Spanish soccer behind Real Madrid and Barcelona, is trying to win its first title and avenge the heartbreaking losses to Real Madrid in a penalty shootout last year and after extra time in 2014. Atlético also lost the final in 1974, to Bayern Munich.

Tuesday’s loss at Bernabéu was the first for Atlético in 16 away games.