Prince Louis joined his brother and sister Prince George and Princess Charlotte on the Buckingham Palace balcony for Trooping the Colour.
They waved at crowds outside the palace and RAF planes making their flypast.
The event, which involved marks the official Birthday of the Queen, involves over 1400 officers and infantrymen on parade.
Report by Carrf.
Like us on Facebook at http://www.facebook.com/itn and follow us on Twitter at http://twitter.com/itn