But before stepping out for his debut appearance, the young prince was spotted looking out one of the windows with his big sister Princess Charlotte by his side.
The siblings looked adorable as they waved and smiled to the crowds who were watching from below.
Shortly after, the children joined their parents, the Duke and Duchess of Cambridge, and the rest of the royal family on the balcony of Buckingham Palace for the past.
Prince Louis watched on in amazement as he sat in his mother's arm, before reaching out for his father, Prince William.
Meanwhile, Prince George and Princess Charlotte appeared to be on their best behaviour.
Missing from today's event was baby Archie Harrison. The newest member of the royal family stayed home while his parents, the Duke and Duchess of Sussex, joined in the celebrations.
This is the first time Meghan has left her son's side since giving birth on May 6.
The new mum wowed fans as she arrived at Buckingham Palace alongside Prince Harry, Kate Middleton and the Duchess of Cornwall earlier today.
Princess Charlotte first attended the royal occasion in 2016 when she was 13 months old (which is a similar age to Louis' now).
Both George and Charlotte were on the balcony at last year's event, however at just 10 months old, Louis was deemed too young to join the festivities.
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