Jens Stoltenberg, Nato secretary general, was accompanied by other key members of the international alliance during a tour of the 65,000-tonne aircraft carrier.
The mighty warship, the biggest ever built for the Royal Navy, is on her first operational mission, having set sail from Portsmouth on Saturday evening.
HMS Queen Elizabeth is currently operating close to the coast of Portugal and is taking part in a Nato exercise called Steadfast Defender 21, the alliance’s biggest war game this year.
Mr Stoltenberg said HMS Queen Elizabeth was a powerful demonstration of the United Kingdom’s vital contribution to Nato.
‘The first aircraft carrier in the world designed to operate fifth generation combat aircraft – from these decks, the Queen Elizabeth projects power to keep us all safe,’ he said.
‘She carries US Marines. She is protected by a Dutch frigate and she is on her way to the Pacific. So this is a perfect example of Europe and North America working together in Nato or our collective security,’
Exercise Steadfast Defender, which runs from May 12 to June 22 is Nato’s biggest exercise this year.
It aims to test the alliance’s readiness and military mobility, with forces deploying across land and sea, from North America to the Black Sea region and off the coast of Portugal.
Twenty ships, 60 aircraft, 500 vehicles and over 9,000 personnel participate in the exercise, which Mr Stoltenberg said ‘reflects Nato’s resolve to deter and defend across the Euro-Atlantic area’.
The exercise also involves the deployment of Nato’s 4,000-strong high readiness force to Romania and the simulated rapid movement of allied forces and equipment across Europe.
First Sea Lord Admiral Tony Radakin, who is aboard HMS Queen Elizabeth, said the drill showed the ‘extremely strong bond between Europe and North America’.
‘It’s focused on the reinforcement of continental Europe from North America,’ the First Sea Lord said. ‘It demonstrates the value of North America and Europe working together and It will strengthen the readiness and deterrence posture of allied command operations through the rapid deployment of reinforcements from North America, movement across the European continent and integration of modern international troops.
‘Secretary general, this really is a special delight to welcome you to our new aircraft carrier. In the same way that the UK provides its nuclear deterrent to Nato, that is the ambition with our aircraft carriers – and you really should see this as your carrier.
‘Nato is implementing the biggest boost of its collective defence in a generation, this exercise takes that a step further and reinforces our collective defence.’
HMS Queen Elizabeth is on a 28-week deployment to the Far East and back as part of Britain’s new carrier strike group.