It was a big moment for a little royal, as he made his debut on the balcony of Buckingham Palace to help celebrate his great-grandmother's official birthday.
At just over a year old, Prince Louis more than rose to the occasion as he charmed the world with his first, very enthusiastic, royal wave.
The third child of the Duke and Duchess of Cambridge pointed to the fly-past overhead, waved at crowds below and politely clapped the national anthem as he the stole the show at Trooping the Colour, where the Royal family turned out to honour the Queen and her Armed Forces.
The Duchess of Sussex, who gave birth to her son Archie just over a month ago, made her return to public life, joining the carriage procession and balcony appearance alongside the Duke. The Duchess, who missed President Donald Trump's state visit because she was on maternity leave, looked well, riding with the Duchesses of Cornwall and Cambridge, and Prince Harry.
Archie Mountbatten-Windsor, the 5-week-old son of the Duke and Duchess of Sussex, was not seen in public at the ceremony.
For the balcony appearance, always a highlight of the Queen's official birthday parade, at least 44 members of the family squeezed together in a rainbow of colour to greet the large crowds.
The Queen, wearing a pastel tweed dress in shades of pale pink, mint, yellow and gold, and the badge of the Brigade of Guards, took centre stage. As the day drew to a close, she beamed as the public cheered.
In a moment of history, Trooper Nina Croker became the first woman in the Household Cavalry to ride in the ceremony.