Both teams finished runners-up in their respective groups, with goal difference being the deciding factor for both sides.
Here, the PA news agency looks at the main talking points of the Johan Cruyff Arena clash.
Wales fans’ ban
The build-up to the game has been dominated by the banning of Wales fans as the United Kingdom is not on Holland’s safe list of countries.
Neither is Denmark, but Danish fans are able to attend.
This is because of a rule which allows European Union and Schengen area residents exemption to the entry rules and the need to quarantine.
Denmark fans can avoid quarantine in Holland by spending less than 12 hours in the country – and around 4,400 of them are expected in a 16,000 Amsterdam crowd.
The same exemption does not apply to Wales fans following the UK’s withdrawal from the EU.
Can Bale end drought?
There is no denying Gareth Bale is Wales’ talisman and leader.
The Real Madrid forward is the player every member of the Wales squad looks to for inspiration after what he has achieved for club and country.
Bale shone in France five years ago when Wales reached the semi-finals and he has had his moments at Euro 2020 with two outstanding assists in the 2-0 win over Turkey.
But Bale also blazed over a penalty in that game and has now gone 14 games without scoring for his country.
Amsterdam would be a perfect place to end that drought.
Denmark the ‘People’s Favourites’
Wales were many fans’ second favourite team at Euro 2016 – a nation of only three million people making the last four after ending a 58-year wait to play at a major tournament.
The so-called ‘Red Wall’ were also given an “outstanding contribution” award from UEFA for their part at the tournament.
But the mantle of ‘People’s Favourite’ has passed to Denmark at Euro 2020 after midfielder Christian Eriksen suffered a cardiac arrest in their tournament opener against Finland.
More Kieffer boosts Wales
Kieffer Moore’s importance to Wales was underlined in their final group game against Italy – when he was dropped.
Moore was on a booking and boss Robert Page feared another one to rule the Cardiff striker out of the round of 16.
He was eventually summoned as Wales went down to 10 men and a pressure-releasing option was needed.
Bale welcomed Moore’s arrival by urging him not to get booked and Page told him “to jump with no arms”.
With such restrictions removed in Amsterdam, Wales hope the 6ft 5in targetman can trouble Denmark’s three-man defence.
Danes hold the edge in past meetings
Denmark have won six of the 10 games between the countries. Wales have four wins with no draws.
Craig Bellamy twice scored a winner in the fixture – in games 10 years apart.
Bellamy grabbed a late decider in a Euro qualifying in Copenhagen in October 1998, and repeated the feat in a 1-0 Wales victory in a 2008 friendly.
Denmark won their first meeting – a 1966 World Cup qualifier – as well as the last two.
Eriksen starred as Denmark claimed a 2018 Nations League double by winning 2-0 in Aarhus and 2-1 in Cardiff.