The palace said Philip's admission was taken on the advice of his doctor, and he is expected to remain through the weekend and into next week for observation and rest.
Philip walked into the hospital unaided after arriving by car, and the palace has said he was admitted out of “an abundance of caution.”
Philip, who retired from public duties in 2017, rarely appears in public. His most recent public event was a military ceremony at Buckingham Palace in July.
During England’s current coronavirus lockdown, the duke has been staying at Windsor Castle, west of London, with the queen, who has performed duties such as meetings with dignitaries remotely.
The royal household is planning celebrations to mark Philip’s 100th birthday on June 10, lockdown restrictions permitting.
Philip married the then-Princess Elizabeth in 1947 and is the longest-serving royal consort in British history. He and the queen have four children, eight grandchildren and nine great-grandchildren.