The Duchess of Cambridge is known for her love of dressing her children in royal hand-me-downs. The tiny tot was adorable as he and his siblings - 5-year-old Prince George and 3-year-old Princess Charlotte - all waved atop the Buckingham Palace balcony.
At six weeks old, Prince Louis didn't attend last year's Trooping the Colour as he was too young, which is the same reason Prince Harry and Meghan Markle's one-month-old baby Archie Mountbatten-Windsor also missed out on the festivities this time around.
Yesterday marked Prince Louis' first royal engagement when he attended Trooping the Colour, wearing the same top as his uncle, Prince Harry, did in 1986.
The ceremony sees 1,400 soldiers, 200 horses and 400 musicians parade central London to celebrate the monarch's birthday.
Louis, who only last month was shown in pictures walking for the first time, appears to be a natural as he lapped up the applause from thousands of royal fans outside the palace gates.
EA Play 2019 - Star Wars Jedi Fallen Order Gameplay Demo
Traversing the environment was similar to many other games of the genre whether it was swinging from vines or climbing up walls. In the bottom middle part of the screen, a force meter depletes and refills anytime Cal uses Jedi abilities.
Before everyone knew it, Louis's first balcony appearance was over and the royals headed back into Buckingham Palace for a special reception.
Princess Charlotte, now four, made her debut in 2016, and her big brother Prince George, now five, in 2015.
The Duchess of Sussex showed off the flashy addition while making her first public appearance since the birth of her son Archie.
It is thought to be a "push present", a gift given by a husband to his wife after the birth of a child.
She was not among royals who met US President Donald Trump during his state visit to Britain earlier in the week.
She is expected to follow the lead of her sister-in-law the Duchess of Cambridge and attend a "few engagements" over the coming months, just as Kate did last summer following the birth of Prince Louis in April a year ago.