It included a series of photos showing Anne carrying out her royal duties and one of her and Her Majesty.
Meanwhile, Clarence House – the residence of Prince Charles and Camilla – also paid tribute to Anne.
Wishing The Princess Royal a very Happy Birthday today. 🎂
In this photo from 1951, The Prince of Wales squeezes his younger sister’s hand while sitting in their prams in the Clarence House garden.
— The Prince of Wales and The Duchess of Cornwall (@ClarenceHouse) August 15, 2021
The post read: “Wishing The Princess Royal a very Happy Birthday today.”
It included a throwback image of Anne and brother Charles when they were children back in 1951.
The post added: “In this photo from 1951, The Prince of Wales squeezes his younger sister’s hand while sitting in their prams in the Clarence House garden.”
Royal fans gushed over the picture as one said: “Aww what a sweet picture. I wish the Princess Royal a super happy birthday.”
Another wrote: “Awww that’s a heartwarming picture. Happy 71st birthday HRH!”
A third added: “What a fab pic. Many happy to Princess Royal.”
Other fans have paid tribute to Anne, with many calling her one of the “hardest working” members of the Royal Family.
One person said: “Happy 71st Birthday to the hardest working royal Princess Anne.”
Another tweeted: “Happy Birthday indeed to Princess Anne. One of our hard-working Royals.”