Azzam, which was built by German firm Lurssen, is a staggering 590 feet long - a £400million floating palace which has knocked Roman Abramovich off the owners' top spot.
This is the moment the world's largest private yacht took to the sea.
It was officially unveiled for the first time in April following three years at the shipbuilder's docks in Bremen.
World beater: The yacht Azzam is 590 feet long and cost a staggering £400million
Yachtspotters have now photographed Azzam, believed to have been ordered by a Middle-Eastern billionaire, being tested on the North Sea.
Azzam has taken pole position as the world's largest yacht off Eclipse, a 533-foot boat owned by Roman Abramovich.
It can travel in excess of 30 knots, with power coming from a combination of two gas turbines and two diesel engines with a total of 94,000 horsepower.
Majestic: Believed to have been pictured in the North Sea, the yacht was first unveiled back in April
Speed as well as size: Experts claim the megayacht reached a speed of 31.5 knots during its trials - making it by far the fastest in the world
Peter Seyfferth, from TheYachtPhoto.com, said: "During the three days of trials, Azzam reached an amazing top speed of 31.5 knots, making her not only the longest but also by far the fastest megayacht in the world.
Such a speed is absolutely exceptional for a yacht of this size."
Labour of love: The megayacht spent three years at the shipbuilder's docks in Bremen, and has been praised for its sleek lines.
"Her elegant, sleek lines are another feature which distinguish Azzam from all the other yachts above 150 metres."
Mubarak Saad al Ahbabi was the engineer behind the megayacht, and assembled a team to work on the ultra-sophisticated project.
Ready to serve: The vessel will be delivered to its owner, believed to be a Middle-Eastern billionaire, later in 2013
He was told by the yacht's secret buyer to build a vessel which was innovative and had a timeless design which would be able to travel at high speed and in shallow waters.
The exterior design, which has been described as 'surprisingly slender' was carried out by Nauta Yachts, with interior designer Christophe Leoni working on Azzam's inside. Azzam is expected to be delivered to its owner later this year.