The Royal Navy's £3.1bn new aircraft carrier has been commissioned at a ceremony in Portsmouth attended by the Prince of Wales and Duchess of Cornwall.
They inspected a royal guard made up by the ship's company, as part of the event at the city's naval dockyard.
The Duchess of Cornwall, who is the ship's sponsor, told the gathering of about 3,000 people that it is "the beginning of an exciting new era in our long naval history".
The hoisting of the white ensign officially designated the ship as part of the Royal Navy's operational fleet.
The carrier, which is taller than Nelson's Column and has a flight deck the size of three football pitches, will have at least 700 people serving on board and the capacity to hold around 1,600 personnel.
A service was conducted by the chaplain of the fleet, with music from the Band of the Royal Marines.
The carrier is the eighth Royal Navy vessel to bear the name HMS Prince of Wales.
The 65,000-tonne warship was united with its sister ship, HMS Queen Elizabeth earlier this month, when the older of the pair returned from the US, where it had been carrying out trials of its F35B Lightning jet fighters.
The two 919ft (280m) long aircraft carriers, which cost £3.1lbn each, are expected to be in service for the next 50 years and are the largest and most advanced warships ever built for the navy.
Major upgrade work has been carried out on the jetties at Portsmouth to allow the ships to berth beside each other.
The duchess' role as sponsor is "akin to being a godmother", according to a navy spokeswoman, and means she will attend significant events "during the life of the ship".