Portugal and Israel are among the permitted destinations on the government's green list, which tourists will be able to visit without having to quarantine on their return.
Countries are in three categories - green, amber and red. Green countries have the fewest rules.
Their status depends partly on the number of Covid-19 cases in each country and the success of their vaccine rollout.
Scotland, Wales and Northern Ireland have not yet announced plans to restart foreign holidays.
The government advises that not all the green list destinations are currently open to UK tourists and it is travellers' responsibility to check.
For example, travel to mainland Portugal and the Azores is currently for essential purposes only. This could change, as in March the Portuguese government said it hoped to welcome UK tourists in May.
The 12 countries and territories on the green list are:
* Portugal
* Israel
* Singapore
* Australia
* New Zealand
* Brunei
* Iceland
* Gibraltar
* Falkland Islands
* Faroe Islands
* South Georgia and the Sandwich Islands
* St Helena, Tristan de Cunha and Ascension Island
The list will be reviewed every three weeks. Countries can be added or removed at short notice.
Travellers will need to:
* Take a private Covid test in their holiday destination before returning home - this can be a lateral flow or PCR test
* Fill in a passenger locator form online before leaving their destination
* Take a private PCR test on or before day two of their arrival in England
There will be no need to quarantine when back home, or take additional tests, unless the post-arrival test is positive.
The cost of private PCR tests vary between suppliers, but the transport secretary said he hoped prices could come down to less than £50 per person. Tui Group is offering test packages for between £20 and £90.
People should not be travelling to amber countries for leisure.
Travellers must:
* Take a private Covid test before returning to England
* Fill in a passenger locator form online before heading home
* Self-isolate at home for 10 days
* Take a private PCR test on or before day two of their arrival in England and again on day eight
They could end self-isolation early by taking an optional PCR test on day five, under the existing test to release scheme.
You should not be travelling to red countries for leisure.
Forty-three countries are now on the red list, including Turkey, India, Pakistan, Nepal, the Maldives, Brazil and South Africa.
People can only enter the UK if they are a UK or Irish national (or UK resident).
Travellers must:
* Take a private Covid test before returning to England
* Fill in a passenger locator form online before they head home
* Book a 10-day hotel quarantine and testing package for each member of their group before departure
* Take a private PCR test on or before day two of their arrival in England and again on day eight
Countries can be added to the red list at short notice. If a country's status changes while you are visiting, you would have to follow the stricter rules on your return.
* The European Commission has recommended allowing travel for anyone who has received the last dose of an EU-approved vaccine at least two weeks beforehand. Vaccines used in the UK would qualify
* Greece's tourism minister tweeted that tourism will reopen on 14 May, but with five security levels
* Portugal and Cyprus hope to welcome UK tourists from mid May
* Spain hopes to open up from June
* France says tourists with a French Covid-19 "health pass" (TousAntiCovid) will be allowed from 9 June
From 17 May, the main NHS app will include a feature allowing users to demonstrate they have had two vaccine doses.
It's hoped the app can be used as proof of vaccination when people holiday abroad. A letter can also be requested.
The app is not the same as the NHS Covid-19 one - currently used for contact tracing.
Holidaying in England, Scotland and Wales is now possible, but there are still rules to follow.
At the moment, people in England face a £5,000 fine for having a holiday abroad and must fill in a travel declaration form with a valid reason for their journey.
Before travelling:
You must take a Covid-19 test (in the three days before your departure).
You must book and pay for two PCR tests for your UK quarantine, unless you are exempt and complete a passenger locator form.
Upon arrival:
You must travel directly to your home/place you're staying and not leave for 10 days.
Only use public transport if you have no other option.
Day one of quarantine is your first full 24-hour day in the UK. Rule-breaking fines are £10,000.
Common Travel Area arrivals (Ireland, Channel Islands, Isle of Man) do not have to arrange tests, fill out the locator form or quarantine.
There is separate advice for quarantining in:
* Scotland
* Wales
* Northern Ireland
Anyone allowed to enter England from a red list country (or who has passed through one in the previous 10 days) must quarantine for 10 full days in a managed facility, rather than a private address.
You will need to agree to book and pay for a quarantine package in advance.
* 10-day (11-night) rate for one adult in one room is £1,750
* Additional rate for one adult (or child over 11) is £650
* Children aged five to 11 are charged £325
You can be fined £10,000 or jailed for not providing accurate details of countries you visited.