The Duke of Edinburgh, who will be 91 on Sunday, was taken to King Edward VII Hospital in London from Windsor Castle "as a precautionary measure after developing a bladder infection, which is being assessed and treated," the palace said in a statement.
The queen's husband will remain hospitalized and under observation "for a few days," the statement said.
Prince Charles noted his father's illness while addressing thousands who packed the Buckingham Palace grounds for a concert Monday night featuring music legends including Elton John and Stevie Wonder.
"The only sad thing about this evening is that my father couldn't be here with us," the prince said. "Because unfortunately, he has taken unwell."
Charles then asked the concertgoers to send his father a message, saying, "If we shout loud enough, he might just hear us in (the) hospital."
The crowd responded with a roar, which segued into chants of "Philip! Philip!"
In addition to the concert, Philip will miss Tuesday's service of thanksgiving, luncheon and carriage procession marking the 60th anniversary of Elizabeth's coronation. "He is, understandably, disappointed," the palace said.
Paul McCartney, one of the performers Monday night, addressed fans outside Buckingham Palace after news of Philip's hospitalization broke, wishing the prince a speedy recovery.
In December, Philip spent four nights, including Christmas Eve and Christmas, in Papworth Hospital being treated for a blocked coronary artery.
When Philip turned 90 last year, he said he would gradually "wind down" his workload.
"I reckon I've done my bit. I want to enjoy myself now ... have less responsibility, less frantic rushing about, less preparation, less trying to think of something to say," he told the BBC in an interview.
The longest-serving consort in British history, Philip married then-Princess Elizabeth in November 1947 in Westminster Abbey. They had two children, Prince Charles and Princess Anne, before she acceded to the throne, and two afterward -- Prince Andrew and Prince Edward. They have eight grandchildren.
Born the prince of Greece and Denmark on the Greek island of Corfu in 1921, Philip left Greece with his family when he was 18 months old after King Constantine was forced to abdicate the throne following a revolution. The family moved to Paris and then England in 1928, and Philip also went to school in Germany.
Philip renounced his Greek title when he became a naturalized British subject in 1947.
He joined the Royal Navy in 1939, and met Elizabeth in July that year when she visited the Royal Navy College in Dartmouth with her father, King George VI.
After Princess Elizabeth became queen, Philip gave up his naval career to support her and embarked on a long career of charity work, notable for its initiatives for young people.
Both he and the queen are great-great-grandchildren of Queen Victoria, and are also related through his father's side -- his paternal grandfather, King George I of Greece, was Queen Alexandra's brother.
Philip has made more than 5,000 public speeches during his working life, according to Buckingham Palace.