Princess Anne’s trip to Canada that was due to begin at the end of this week has been postponed.
She was injured when she was out walking on her estate and horses were nearby.
The cause of her head injury is unconfirmed.
Emergency services were called to the estate and the princess was taken to Southmead Hospital, Bristol.
She is expected to stay in hospital until later this week “as a precautionary measure for observation”, a Buckingham Palace statement said.
Her husband Admiral Sir Tim Laurence and her daughter Zara and son Peter were on the estate at the time. Her husband then travelled with her to hospital.
In a statement, Buckingham Palace said: “The Princess Royal has sustained minor injuries and concussion following an incident on the Gatcombe Park estate yesterday evening.”
Princess Anne has been known as one of the most hard working royals, carrying out many engagements.
Her sense of public duty combined with a no-nonsense approach has helped her status as one of the most popular royals, with consistently high approval ratings in opinion polls.
She is known for her interest in horses and her achievements in equestrian sports, becoming the first member of the Royal Family to compete in the Olympics, in the games in Montreal in 1976.
As the second child of Elizabeth II and Prince Philip she was third in line to the throne when she was born and she is now 17th in the line of succession.
She has married twice. Her first husband, Captain Mark Phillips, is the father of her two children, Peter and Zara.
