The winger scored twice in the first 10 minutes to put Carlo Ancelotti’s side in control in Saudi Arabia. Robert Lewandowski pulled one back for Barca with a superb volley but Vinicius converted a 39th-minute penalty to restore Los Blancos’ two-goal lead.
Rodrygo then added a fourth in the second half before Ronald Araujo was sent off to complete Barca’s misery.
Vinicius, who has recently returned from tearing a hamstring in November, celebrated his opener with Cristiano Ronaldo’s famous ‘SIU’ goal celebration inside Al Nassr’s King Saud University Stadium – where the former Real Madrid man currently plays.
He said: “The celebration was dedicated to Cristiano Ronaldo, because he is my idol and now he plays here.”
Victory was Madrid’s third straight in El Clasico and gave them a 13th Super Cup success – one behind Barcelona’s record 14 wins.
Jude Bellingham was key to the opening goal, playing the ball in behind the high line of Barcelona for Vinicius to race on to and round goalkeeper Inaki Pena to score.
Three minutes later it was Rodrygo timing his run in behind to perfection to expose Xavi’s side before crossing for Vinicius to slide in at the back post.
Barca responded well and got themselves back into the game when Alejandro Balde’s cross was only headed out to the edge of the box, allowing Lewandowski to thump in a first-time finish.
But just a few minutes later, the referee adjudged that Vinicius had been pulled down in the box by Araujo as he tried to get on the end of a cross.
Complaints from Barca were ignored and the 23-year-old Brazil international confidently slotted home the spot-kick to complete his second Madrid hat-trick.
With Barca throwing players forward to try and get back into the match after half-time, Madrid continued to threaten on the break and Rodrygo capitalised on some sloppy defending to stroke in the fourth.
It got worse for Barcelona as Araujo’s frustrations got the better of him and he scythed down Vinicius to earn himself a second yellow card with 20 minutes remaining.
Bellingham had a shot cleared off the line as Madrid went in search of a fifth but Barca avoided any further punishment in the closing stages.
“We have not shown the level required for a match like this,” Barcelona Xavi said.
“We played our worst game. We weren’t comfortable at any point. Madrid hurt us on the counter. I apologise to the fans because it was hard for us to compete and we showed our worst side.”