The prince, whose official title is the Duke of Edinburgh, walked into London’s private King Edward VII Hospital without assistance after feeling unwell for a short time, a royal source said.
The queen, 94, lives at Windsor Castle near London, where the couple lived during the British coronavirus pandemic. Both received their first dose of COVID-19 vaccine in January.
“The Duke’s admission is a precautionary measure, on the advice of the doctor of His Royal Highness, after he felt unwell,” Buckingham Palace said in a statement.
“The duke is expected to remain in hospital for a few days of observation and rest.”
A royal source said Philip did not have a COVID-19 disease and that it was not an emergency.
Within an hour of his arrival, cameramen and photographers from Britain, Australia, France and Germany gathered outside the hospital where policemen were waiting.
“Really sorry to hear that His Royal Highness, the Duke of Edinburgh is in hospital,” said British Health Minister Matt Hancock. “I send my best wishes for a speedy recovery.”
A former naval officer known for his sometimes brutal manner and humor, she married Elizabeth in 1947, five years before she became queen. He is now by far the longest company of any British monarch.
Philip is now rarely seen in public. He stepped down from official commitment in August 2017 after completing more than 22,000 solo events and thousands more with the Queen.
During the pandemic, the royal family visited hospitals and frontline workers, either online or in person, to thank them for their efforts. Prince Charles, the successor to the throne, visited staff at a hospital in Birmingham earlier on Wednesday.
The royal family has also been in the news in recent days after Philip’s grandson Prince Harry and his American wife Meghan announced that they were expecting their second child, and that they had agreed to an interview with Oprah Winfrey.
Some of the topics they will be discussing are why the couple left the royal family to spend more time in America last year.
Greek-born Philip has had several hospitals over the past decade, including treatment for an infection in 2017 and hip replacement surgeries. He was admitted to hospital earlier in late 2019.
The duke is due to turn 100 in June. The pony newspapers reported that he did not want any public uproar.