A smiling and apparently fit Queen Elizabeth left hospital on Monday a day after she was admitted with symptoms of gastroenteritis.
The 86-year-old British monarch, wearing a red coat and silver brooch, shook hands with medical staff on the steps of the King Edward VII hospital in central London before being driven away by limousine.
Buckingham Palace officials said she had first developed symptoms of the stomach bug on Friday and the decision to take her to hospital was a precautionary measure.
Royal aides suggested at the time she might stay in for a couple of days.
The palace offered no further details on the queen's condition, but confirmed that all her engagements for this week, including a trip to Italy scheduled for March 6-7, remained canceled or postponed.
It is unusual for the monarch to cancel an engagement.
The head of state, who last year celebrated 60 years on the throne, is known for her robust health. She was last hospitalized in 2003 when she had a knee operation.
News of her latest hospital admission made headlines around the world.
The queen and the royal family have enjoyed a surge in popular support in Britain in recent years, spurred on by the wedding of her grandson Prince William to Kate Middleton in 2011.
The couple, now known as the Duke and Duchess of Cambridge, are expecting a child this summer.
The queen's own Diamond Jubilee celebrations last year cemented her popularity, as did her participation in the opening ceremony of the London Olympic Games, appearing alongside the fictional spy James Bond in a video sequence hailed as one of the highlights of the show.