There was a dazzling on-pitch light show to accompany Williams and opera star Garifullina, with performers dressed in the colors of each of the 32 World Cup teams bopping to the music.
Around 500 dancers, gymnasts and trampolinists will also be performing in an opening ceremony that will pay homage to all things Russian.
It is across the river from Luzhniki Stadium, which will host seven games at the World Cup, including the opening game on June 14 and final on July 15.
After billions of dollars spent, new stadiums built and much anticipation, the 2018 World Cup got underway with a musical opening ceremony.
"We are sincerely happy to host the World Cup in our country", said Putin.
For the Russian Federation 2018 World Cup opening ceremony, FIFA has announced that Robbie Williams and Aida Garifullina will grace the stadium to bless guests and viewers worldwide with noteworthy musical performances.
Stephen Doughty, a Labour MP on the Home Affairs Committee looking into the suspicious deaths of Russians on British soil, said on Monday that it was "surprising and disappointing" that Williams had "agreed to be paid by Russia and Fifa".
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The football chief said "scammers" had "deceived me into thinking they were genuine persons interested in investing in our country".
It was hard to miss - Williams did it right into the camera that was in front of him while singing his hit "Rock DJ".
While the Russian Federation has passed laws on public obscenity in recent years, it's unlikely Williams will be disciplined by authorities - unless he attempts to duplicate the performance in the near future.
"Robbie Williams just flipped off the camera on the most watched event in the world", tweeted one observer.
Williams and Garifullina then joined forces for a duet of his single Angels as the crowd at Moscow's Luzhniki Stadium sang along.
Russian Federation went on to win the opening game 5-0 against Saudi Arabia.