In a speech to the British parliament on Monday, May laid out the UK's offer to EU nationals living in the country after Brexit.
She also made key pledges on pensions and health that will be of interest to British nationals living in Spain and other EU countries.
May said the British government will continue uprating pensions, meaning they will not be frozen as they are for elderly British nationals living in countries like Canada and Australia.
The Conservative prime minister, who has been under fire ever since her party's near-disastrous election result earlier this month, also vowed that payment of disability benefits and health cover would continue for Brits in the EU after Brexit.
“The UK will continue to export and uprate the UK state pension and provide associated healthcare cover within the EU,” May told parliament.
“We will continue to protect the export of other benefits and associated healthcare cover where the individual is in receipt of those benefits on the cut-off date," she added.
That cut-off date has not yet been set but will be some point between the triggering of Article 50 on March 29th this year, which officially signalled the UK's intention to leave the EU and March 29th 2019.
Theresa May also said the UK intended to continue to be a part of the European Health Insurance Card Scheme, so Brits who travel to Spain and other EU countries can continue to the health costs covered.
For longer-term residents it would mean continuing with a system whereby each country reimburses the other for the healthcare costs incurred by their citizens.
The issues of health and pensions have high on the list of Brexit worries for British nationals ever since the UK voted to leave the EU in June last year.
The bulk of May's speech on Monday laid out the UK's offer to EU nationals living in the UK.
All EU nationals who have five years' continuous residence in the UK will be eligible to apply for “settled status”.
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