The portrait was reshared on the royal family's social media accounts, with the caption: "Wishing Prince George a very happy 8th birthday today!"
WATCH: William and Kate share a new photo of Prince George for eighth birthday
The photograph, taken by mum Kate earlier this month at the Cambridges' Norfolk home, shows George grinning at the camera, as he sits on the hood of Land Rover Defender - a sweet nod to his late great-grandfather, the Duke of Edinburgh.
George is the Queen's third oldest great-grandchild, after his cousins, Savannah and Isla Phillips.
In 2016, Kate revealed that her son has a sweet nickname for his great-grandmother. At the time, the Duchess said: "George is only two-and-a-half and he calls her 'Gan-Gan.' She always leaves a little gift or something in their room when we go and stay and that just shows her love for her family."
Prince George grins in his official birthday photo
The Cambridges watched the Euro 2020 final at Wembley Stadium
His last public appearance was at the Euro 2020 final with his parents but sadly it was commiserations for the England team as they were defeated by Italy in a penalty shootout at Wembley Stadium.
Football-fan George currently attends Thomas's Battersea School in south-west London, along with Princess Charlotte.
The couple recently celebrated their first wedding anniversary after tying the knot in a private Windsor ceremony last July.
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