Dressed in a cream-colored outfit, the Queen, 87, arrived at a private hospital at just before 7 – four full days since he was first admitted.
Earlier in the day, Philip's youngest son, Prince Edward, 49, had been to see him. Asked how his father was, Edward told reporters, "[He's] well, thank you."
Philip, who is said to be "comfortable and in good spirits," underwent an exploratory operation on Friday and spent the weekend being cared for at the London Clinic.
In a statement regarding his progress, Buckingham Palace suggested that the prince is to spend two months convalescing from his hospital stay.
About half an hour before the Queen's arrival, her personal physician Professor John Cunningham was seen entering the London Clinic, and she was kept informed about her husband's progress while staying at Windsor Castle over the weekend.
Also on Monday, various gun salutes sounded around the U.K. in honor of the Philip's birthday. A 41-gun salute took place in Green Park, near Buckingham Palace, while 62 guns went off at the Tower of London.