British tourists will be allowed to enter Portugal from next Monday, the Portuguese authorities have announced.
Portugal is on the UK's "green" list for unrestricted travel from then, but there had been confusion over whether the Portuguese would reciprocate.
Coronavirus is still causing concern in Portugal and the country has extended its state of calamity to 30 May.
The government in Lisbon said anyone arriving would need to take a negative PCR test before departure.
The announcement was made by the Portuguese foreign ministry, which said tourism authorities had been ensuring that testing capacity in Portugal will meet the demand from tourists.
"With an air capacity from (at least) 21 airports in the United Kingdom into Portugal, reinforced due to the high demand from this market, the options are wide for the British tourists to visit Portugal from any point," the ministry said.
"People from the United Kingdom have visited Portugal and celebrated our culture, traditions, landmarks, history, and enjoyed our warm hospitality for decades. We look forward to welcome all travellers coming from the UK."
The Portuguese announcement followed days of uncertainty and confusion over whether thousands of holidays booked by UK travellers from Monday would in fact go ahead.
On Thursday, it looked as though many holidaymakers' hopes would be dashed when Portugal extended its Covid emergency measures.
But to widespread relief, the Lisbon government has now given its approval to UK tourists.
Authorities in the UK had already announced that travellers from England and Scotland would not have to quarantine on their return from Portugal and other "green list" countries from 17 May.
However, those countries have their own restrictions on who can visit.
'I'm super-desperate to go away'
As an NHS worker, 32-year-old Rebecca Morgan, of Bow in east London, has gone beyond the call of duty during the pandemic.
Instead of taking her annual leave over the past year, she has been doing extra shifts on Covid wards.
But now she feels it really is time for a break - which is why she plans to fly to Faro in Portugal on 31 May for a week's holiday.
"I'm super-desperate to go away," she told the BBC. "I've not had a proper week off for a year and a half. I'm really looking forward to having a good lie down on the beach."
Rebecca is expecting to pay £400 for the three required PCR tests and would have preferred the option to isolate at home.
"The cost of the tests will probably cost more than the holiday," she says.
"I'm tested twice a week for work, had Covid back in January and I've had both vaccines now, so I'm not expecting to get Covid at this stage."
At present, Portugal allows flights to and from the UK, but only for essential travel, such as for business, study, family reasons, health or humanitarian reasons.
Those travel restrictions will be lifted only from 17 May.
Tui has 44 flights due to depart for Portugal between 17 and 30 May. These include 28 to the Algarve, a popular destination for UK summer holidays.
Other firms, including EasyJet, have been offering holidays and flights to green list countries, but online travel firm On The Beach has stopped selling all holidays for this summer because of Covid uncertainty.
EasyJet said: "We welcome the decision from the Portuguese government meaning that those travelling from the UK will be allowed to travel safely to Portugal from Monday.
"We look forward to reuniting friends and family and taking customers on a long-awaited holiday this summer."
The Abta travel association said it was "fantastic" that tourists could return to Portugal.
"UK tourism is a really important part of the Portuguese economy, contributing half a billion pounds a year in normal times," an Abta spokesperson said.
At the same time, Greece has launched its tourist season, lifting most remaining restrictions on movement and declaring "we are putting the lockdown behind us".
Although an average of 2,000 daily Covid cases are still being reported, vaccinations are being rolled out with the Greek islands as a priority.