Hundreds of Royal Navy personnel will join forces with warships, submarines and aircraft from 13 other countries for a two-week exercise.
Naval ships, Royal Marines and helicopters from the Fleet Air Arm will be in and around Scotland for Exercise Joint Warrior.
It will see the navy work alongside the Army and Royal Air Force as well as tri-service counterparts from Belgium, Canada, Denmark, Estonia, France, Germany, Italy, Latvia, Lithuania, the Netherlands, Norway, Spain and the US.
In total, there will be 6,500 personnel at sea, 3,000 operating on land and 800 working from helicopters and aircraft.
Joint Warrior, taking place between March 30 and April 11, will see NATO allies carry out warfare scenarios to ensure they are ready to face any threat.
The exercise will be controlled from the Maritime Operations Centre at HMNB Clyde with air, surface, sub-surface and security training taking place off the west coast of Scotland.
Air units will liaise with maritime and land forces to practise intelligence, surveillance and reconnaissance (ISR), defence and attack from multiple RAF bases in the UK while land activity will see units operate at Cape Wrath and the bombing range at Tain.
The Royal Marines will be conducting amphibious landings at Castlemartin Range in Wales.
Defence Secretary Gavin Williamson said: "The UK military is a partner of choice for its major international allies and a resolute force for peace around the world.
"The UK will not waver in continuing to work with its allies to protect our mutual interests.
"Led by the UK, Joint Warrior allows key NATO allies to tackle complex warfare scenarios to ensure the international community stands fit and ready to work to face any threat together."
After an initial briefing weekend at HMNB Clyde, the participating nations will split into two opposing task forces starting in Scotland. As Joint Warrior continues, elements of the task forces will head south for the amphibious exercises off the south-west coast of Wales.