On Friday, the Buckingham Palace account posted a sweet footprint photo to social media, writing, "Her Royal Highness Princess Beatrice and Mr. Edoardo Mapelli Mozzi have named their daughter Sienna Elizabeth Mapelli Mozzi."
Sienna's middle name, Elizabeth, is a tribute to her great grandmother, Queen Elizabeth II.
The Palace added, "The couple have said, 'We are all doing well and Wolfie is the best big brother to Sienna.'"
Edoardo is also dad to son Christopher, 5, who goes by Wolfie, from a previous relationship.
👶 Her Royal Highness Princess Beatrice and Mr Edoardo Mapelli Mozzi have named their daughter Sienna Elizabeth Mapelli Mozzi.
Prior to the Palace sharing the full name, Edoardo, posted an update to his own account, writing, "Our life together has just begun, and I can't wait to see all the amazing things that await us. Feeling so much love and gratitude for my amazing wife, baby Sienna and Wolfie. These are the days I never want to forget. This week, a friend said to me the sweetest saying... that with every child you grow a whole new heart."
Sienna arrived on Saturday, Sept. 18 at 11:42 p.m. GMT at the Chelsea and Westminster Hospital in London, England. She weighed six pounds and two ounces.
"The new baby’s grandparents and great grandparents have all been informed and are delighted with the news," the Palace said at the time. "The family would like to thank all the staff at the hospital for their wonderful care. Her Royal Highness and her child are both doing well, and the couple are looking forward to introducing their daughter to her big brother Christopher Woolf."