Buckingham Palace described the 95-year-old monarch's symptoms as "cold-like", adding that she would continue to carry out "light" duties at Windsor Castle.
Britain's Queen Elizabeth has tested positive for COVID-19, Buckingham Palace has announced.
The palace described her symptoms as "light" and comparable to a cold.
The 95-year-old monarch had recently been in contact with her son Prince Charles, two days before he tested positive for the coronavirus.
The Queen will however continue to carry out "light tasks" at Windsor Castle over the next week, Buckingham Palace explained.
“She will continue to receive medical attention and will follow all the appropriate guidelines," it said in a statement.
The Queen has received three jabs of coronavirus vaccine. There are thought to be several recent virus cases among staff at Windsor, where she is staying.
Prince Charles, 73 — whose 74-year-old wife Camilla, the Duchess of Cornwall and the Queen's daughter-in-law, also tested positive — has since returned to work.
Senior British politicians sent get-well messages. "I’m sure I speak for everyone in wishing Her Majesty The Queen a swift recovery from COVID and a rapid return to vibrant good health," tweeted Prime Minister Boris Johnson.
Other well-wishers included the opposition leader Sir Keir Starmer and London Mayor Sadiq Khan.
Britain’s longest-reigning monarch, Queen Elizabeth reached the milestone of 70 years on the throne on February 6, the anniversary of the death in 1952 of her father King George VI.
She recently returned to public duties following several months off after she was told to rest by her doctors after spending a night in hospital for tests in October. She was forced to cancel appearances at several key events, including Remembrance Sunday services at the COP26 climate conference in Glasgow.
In the past week, she has held audiences virtually and in person.
The Queen is also scheduled to attend a string of in-person public engagements in the coming weeks, including audiences with politicians and diplomats, a diplomatic reception at Windsor on March 2 and the Commonwealth Service at Westminster Abbey on March 14.
On March 29, she has a remembrance service at Westminster Abbey for her husband Prince Philip, who died in April 2021 at the age of 99.
Public celebrations of the Platinum Jubilee are scheduled for June, with festivities including a military parade, a day of horse-racing and neighbourhood parties over a long weekend from June 2-5.
People who test positive for COVID-19 are required to self-isolate for at least five days, though the British government says it plans to lift that requirement for England in the coming week.
The Queen is the latest monarch to catch COVID-19. Queen Margrethe of Denmark, 82, and Spain’s King Felipe VI, 54, both tested positive for the illness earlier in February and had mild symptoms.