Sports fans will need to show a pass proving they have been fully vaccinated or had a negative Covid test to attend large-scale events in Wales from 11 October.
Supporters will be able to use an NHS Covid Pass to show they are vaccinated, or had a negative lateral flow test in the 48 hours before the event.
The Principality Stadium will stage four autumn rugby internationals.
Wales have announced a 74,500 sell-out against New Zealand on 30 October.
This will be followed by matches against South Africa, Fiji and Australia.
The pass will be required for any event at which more than 10,000 people attend. It is also needed for nightclubs, indoor no-seating events with more than 500 people and outdoor no-seating events with more than 4,000 people.
First Minister Mark Drakeford made the announcement as part of the latest review of coronavirus restrictions.
The Welsh Rugby Union (WRU) confirmed proof would be required to attend the four international games this summer.
"Throughout the last 18 months, the Welsh Rugby Union and Principality Stadium have been working to the advice and guidance set out by Welsh Government and Public Health Wales," said a WRU spokesperson.
"The wellbeing of supporters and staff is our top priority and we want all supporters to have the best possible experience in the best rugby stadium in the world.
"Following the most recent announcement by Welsh Government, from 11 October 2021 the NHS Covid pass will become an entry requirement for all events scheduled at Principality Stadium."
The regulations could affect Welsh regional sides Cardiff, Ospreys, Scarlets and Dragons if they attract a five-figure crowd.
The new rules will also affect Championship football matches involving Cardiff City and Swansea City and Wales men's World Cup qualifiers against Belarus and Belgium in November.
The internationals will be staged at the Cardiff City Stadium which has a 33,280 capacity, while the Swansea.com Stadium can hold up to 21,088.
Swansea and Cardiff City play in the English Football League (EFL) but there are currently no requirements set out for Covid passes in England.
The Football Association of Wales (FAW), EFL, Swansea City and Cardiff City have been contacted for comment.
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