Victoria and David Beckham and Sir Elton John were also at Harry and Meghan’s big day.
Other celebrity guests included Oprah Winfrey, Idris Elba, Serena Williams, Carey Mulligan, James Blunt and James Corden.
Barrister Amal Clooney glowed in a bright yellow dress and matching hat.
She walked arm-in-arm with her Hollywood star husband, heartthrob George Clooney.
Spice Girl-turned-fashion designer Victoria Beckham arrived with her husband David.
She wore a dark blue outfit and coral heels and did not flash quite the same megawatt smile as Amal.
Meghan’s on-screen husband Patrick J Adams was among the stars of the drama Suits to arrive.
His character Mike Ross wed Meghan’s alter-ego Rachel in the drama Suits.
The actor, who joked that he thought his co-star was popping out to “get some milk” when her engagement was first announced, was at Windsor to watch his screen-wife marry for real.
He arrived with his wife, actress Troian Bellisario, for the ceremony.
Other Suits stars included Sarah Rafferty, who wore a black dress with dramatic sleeves, Gina Torres, Abigail Spencer and Gabriel Macht.
Tennis champion Williams arrived with her husband Alexis Ohanian, co-founder of Reddit.
Actress Priyanka Chopra and actor Tom Hardy were also there.
Sir Elton, wearing pink glasses, was pictured inside St George’s Chapel.
Hollywood star Elba, accompanied by his fiancee Sabrina Dhowre, beamed as he made his way into the ceremony, under bright sunshine.
Singer Blunt and wife Sofia Wellesley were also among the earliest guests for the big day.
US media magnate and talk show host Winfrey, who wore a pink dress and wide-brimmed hat, walked in just behind Elba.
And actress Mulligan and husband, Mumford & Sons star Marcus Mumford, were also there, as well as singer Joss Stone.
Earlier on Saturday morning, Williams hinted that she would be a guest at the royal nuptials - posting a picture of herself in a towel “getting ready for my friend’s wedding”.
Guests who could also help the couple celebrate later include Ed Sheeran and Ellie Goulding, model Cara Delevingne and former Made In Chelsea star Millie Mackintosh.