Passengers arriving in the UK from Luxembourg from Friday will have to isolate for 14 days after the country was taken off the quarantine-free list.
The government said there had been a “consistent increase” in Covid-19 cases in the country since the end of June.
More than 120,000 Britons visit Luxembourg each year but the Foreign Office now advises against all but essential travel there.
It comes after quarantine for Spain was reimposed on Sunday.
In advice published on Thursday, the Foreign Office said it was not telling Britons already in Luxembourg to leave. Instead it said UK travellers should “follow the advice of the local authorities”.
It said data from the Joint Biosecurity Centre and Public Health England had “indicated