The adorable pictures show Prince Louis outside, sitting and playing in moss.
Being the eldest, George was the first of the Cambridge clan to get birthday portraits, which are also the only set of first birthday photos not taken by his photographer mom.
The young prince is shown wearing a burgundy jumper in two of the shots and a blue sweater with a dog sewn onto it in another.
Last November, in a series of adorable photographs taken to commemorate Prince Charles' the Prince of Wales' 70th birthday, Prince William's father takes huge joy in holding Prince Louis, as the then-6-month-old babe smiles radiantly in his grandfather's arms.
The Queen marked her birthday (the real one - she was born on April 1, 1926) with an Easter Sunday service at Windsor Castle.
In a picture taken in 1983 in Bradfield Southend, a sleepy Kate, now 37, wears a white and green babygrow to attend her best friend Nicola Brown's first birthday party.
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One person said: "William and Catherine, thank you so much for releasing these handsome pictures of your adorable baby boy".
The name Louis was already one of George's middle names and pays tribute to the Prince of Wales's great-uncle, Earl Mountbatten, who was murdered by the IRA.
The new official account for the Duke and Duchess of Sussex - AKA Harry and Meghan - posted a comment on the pic.
Elizabeth became queen in 1952 at the age of 25, meaning she has now reigned for more than 67 years.
"The Duke and Duchess look forward to sharing the exciting news with everyone once they have had an opportunity to celebrate privately as a new family". The 37-year-old duchess clearly has a keen eye for photography, capturing attractive, intimate shots of her family, worthy of going into the official royal photo albums.
The couple recently revealed they will not announce the birth of their first child straight away, as they would like time to "celebrate privately".