But 20 miles east of Windsor, in Wembley, another cherished British institution will be celebrated on the same day — the FA Cup, the world’s oldest national football competition.
Even in the absence of Prince William, who usually attends the final as president of the Football Association — English football’s governing body — Wembley will arguably be a more regal affair than Windsor as a King, or perhaps Kings, will almost certainly be crowned.
Score the winning goal in an FA Cup final, or produce a man-of-the-match performance, and yours is a different destiny.
Much like the British monarchy, the FA Cup has endured troubled times — United did not take part in the competition in 2000, for example — and questions over its relevancy in a modern world is a constant.
But on a big occasion such as Saturday, talk about the decline of a nation’s favorite knockout competition will be put on hold and its place in British society celebrated.
Though the riches and the glamor of the English Premier League and the Champions League has, in the eyes of many, diminished the luster of the competition, for the teams taking part on Saturday — and for their millions of fans — the FA Cup matters.
As former Manchester United striker Dimitar Berbatov told CNN Sport this week: “You will see when they win it the joy, the satisfaction that they’ve won something. Everything matters.”
But unlike the royal wedding — which takes place just over five hours before the Wembley kickoff — this FA Cup final will not be a cultural milestone or a modern fairytale. It is a battle between two English footballing aristocrats.
United, one of the world’s richest clubs and English football’s most successful team, will take on Chelsea, seven-time winners of the competition and a club owned by Russian oligarch Roman Abramovich.
As with all good season-ending finales, or modern Royal Weddings, there will be twists, sub-plots and potential flare-ups.
Much has already been written this season about the animosity between United manager Jose Mourinho and Chelsea boss Antonio Conte.
The Chelsea manager, 48, said he would “not forget” Mourinho’s words, though the Portuguese said this week that the feud between the pair ended after a face-to-face meeting at Old Trafford in February.
Nevertheless, when the pressure is on and both are barking orders to their teams from the sidelines who knows what could happen.
Adding to the intrigue is Conte’s future as Chelsea manager. Many expect this match to be the Italian’s swansong for the Blues — even if he guides his team to victory.
Last year’s Premier League champions finished fifth in the league this season, consequently failing to qualify for the lucrative Champions League. It has been a difficult campaign for Conte and his team following his title-winning debut as Chelsea boss.
Mourinho has enjoyed a relatively more fruitful campaign as United finished second in the league.
Victory on Saturday would earn United a record-equalling 13th FA Cup trophy and secure a third major piece of silverware under Mourinho.
There will be a loser at Wembley and hearts will be broken, which is why the saccharine of a royal wedding and the unpredictability of an FA Cup final, two treasured British events, are the perfect combination rather than an antidote.
Best watched back-to-back to form what is being billed as the biggest TV day of the year in Britain.