Launched in 2013 at a reported cost of $500 million, Azzam heads Boat International's Top 101 list at 180 meters (590 feet) in length.
The plaything of Chelsea FC owner Roman Abramovich, Eclipse measures 162.5 meters (533 feet).
Eclipse is only half a meter longer than this vessel owned by Sheikh Maktoum, the ruler of Dubai. Ross Land/Getty Images Europe/Getty Images for DAGOC
Formerly known as Project Omar, Dilbar was launched this year for Russian billionaire Alisher Usmanov. Measuring 156 meters (511 feet) in length, it has the largest gross tonnage -- the measure of internal volume -- at 15,917 GT, according to Boat International.
Owned by the Sultan of Oman, Al Said was the second longest when launched in 2007, measuring 155 meters (508.53 feet).
Launched in 2012, the 147-meter (482-foot) Topaz is one of several vessels on the list built by German firm Lurssen.
The 147-meter (482-foot) Saudi-owned Prince Abdulaziz was the world's longest superyacht for over two decades following its launch in the mid-1980s.
Russian billionaire Viktor Rashnikov's Ocean Victory (140 meters/459 feet) rounds out the top 10 after El Mahroussa and Yas.
At 141 meters (462 feet) long, Dream Symphony will be the world's largest yacht to be powered by sail alone when it launches.