GETTY / REUTERS
Real Madrid beat Juventus to win the Champions League
Ronaldo proved the difference on a night that saw him net his 600th career goal for club and country.
His prowess earned Real a record 12th European Cup under the roof of Cardiff’s Principality Stadium.
Ronaldo gave Real the lead with a side-footed stroke on 20 minutes.
Mario Mandzukic’s superb control and overhead kick levelled the scores at the break.
But Casemiro’s deflected drive, Ronaldo’s instinctive finish and a Marco Asensio tap-in put the game beyond Juve.
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Hometown boy Gareth Bale, who started on the bench, said: "What an incredible scene. The city has done an immaculate job in hosting a great event," he said.
"To win this at home is a great feeling, it's been a hard season, I've worked tirelessly to get fit and these are your rewards.
"We have made history, we'll enjoy this moment now.. We needed confidence at half-time, and we had to take our chances which we did.
"I was happy to get on."
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Cristiano Ronaldo scored the opener for Real Madrid
Ronaldo said: "I prepared myself for this, you win the biggest prizes because of what you do at the end of the season.
"Zidane gave us a very positive half-time team talk and told us he really believed in us. It has been an incredible end to the season by us. We are the first team to win it two years in a row and I scored two goals.
"It's another record for us and the players deserve it and so do I because I scored twice and I'm the top scorer in the Champions League."
Mario Mandzukic (left) scored Juventus' equaliser
The final in Cardiff – the first in the UK for six years – was played out under a heavy security presence.
The roof was closed at the Principality Stadium as part of the security operations and only heightened the atmosphere inside Wales’ national stadium.
Juve started the brighter and Gonzalo Higuain stung Keylor Navas’ hands early with a rasping drive.
But it was Real who broke first when Rolando collected the ball on the edge of the area and buried his low effort first time.
Juve were not to be pegged back, however, and continued to play the more pressing football.
Casemiro's shot deflected in to make it 2-1 to Real Madrid
And it eventually paid off when Mandzukic collected a Higuain knockdown, controlled off his chest over looped his overhead kick above Navas and into the top corner.
Juve were in the ascendancy but half time came at the wrong time.
For Real came out after the break with renewed vigour and took the lead again when Casemiro’s ranged effort deflected off Sami Khedira and crept into the net.
Moments later and it was 3-1 when Ronaldo burst through an uncharacteristically static Juve defence to tap home Luka Modric’s cut-back.
And to compound Juve’s misery Juan Cuadrado was sent off for a challenge on Sergio Ramos before Asensio tapped home in injury time.