More than 60,000 football fans will be allowed to attend the semi-finals and final of Euro 2020 at Wembley.
They will be the largest crowds at UK sporting events in more than 15 months.
It is not clear exactly how many fans will be let through the turnstiles, but the culture department (DCMS) said attendance would be increased to “75% capacity”, which is 67,500.
All ticket holders for the matches on 6, 7 and 11 July must be able to show a negative COVID-19 test or proof of full vaccination – 14 days before each fixture.
Those registered with a GP in England will be able to display their proof of immunisation via the NHS App, or through a printout for people from Scotland or Wales.
A negative lateral flow test can be shown via email, a text message or the NHS App.
Further details – including on ticket sales – will be given by UEFA in due course, DCMS said.
“It is expected ticket holders in the UK who lost their tickets for the semi-finals and final in the re-ballot will be at the front of the queue to be at the games,” it added.
DCMS said other events in the summer sporting calendar, including Wimbledon, the Challenge Cup Final and men’s international cricket involving England, Pakistan and Sri Lanka will “also go ahead with greater capacities”.
It is part of the government’s Events Research Programme (ERP) as the UK gradually emerges from the coronavirus pandemic.
Up to 20 indoor and outdoor events are also being planned that will “allow audience numbers to return close to full capacity”, DCMS said.
It will “continue to trial the use of COVID status certification” and the pilots “will involve the ramping up of trialling the use of the NHS App and lateral flow testing, as proof of a person’s COVID-status”.
Trials of the NHS App “will be run to assess whether it can also be used to display a user’s natural immunity status”.
There have been reports suggesting the Euro 2020 final could be moved to Budapest following controversy over potentially allowing 2,500 international VIPs to attend without having to quarantine when arriving in the UK.
Italian Prime Minister Mario Draghi has said Rome could be an alternative venue.
But UEFA said there are “no plans to change the venue” for the semi-finals and final.
Culture Secretary Oliver Dowden said “rigorous and tight public health measures remain in place” while allowing “more fans to see the action live”.
He added: “The finals promise to be an unforgettable moment in our national recovery from the pandemic.”
London Mayor Sadiq Khan said the matches will “show that when it comes to great sporting events, London simply cannot be beaten”.