|English||Grand World (Great Sea Route)|
|Romaji||Idainaru Kōro (Gurando Warudo)|
|Located In||Living World|
|Controlled By||World Government|
The Grand World (偉大なる航路（グランドライン） Idainaru Kōro (Gurando Warudo), literally translated as Great Sea Route) is an ocean where the marines and mythical Devil Fruits are situated. The Grand World is made of eighty percent water; making it somewhat difficult to traverse. It is completely an ocean current that is surrounded by the Calm Belts and follows an imaginary line that runs from north-west to south-east across the middle of the world and perpendicular to the Red Line. The Red Line is a vast continent that circles the globe from north-east to south-west. These two lines divide the rest of the Blue Sea into the Blues: North Blue, East Blue, West Blue, and South Blue. This stretch of ocean is said to be the most dangerous place in the world, and is commonly referred to as the Pirates' Graveyard by people from the four Blues because of this reputation (But referred to as "Paradise" for those few who make it to the second half, showing it is all relative). Most believe that it is impossible to safely leave the Grand World save at its beginning and end; however, the World Government regularly sends ships across the Calm Belts by coating their hulls with Kairoseki, rendering them invisible to the Sea Kings.
To the north and south of the Grand World are strips of ocean known as the "Calm Belts". The waters of the Calm Belts remain static year round, and there are virtually no winds or waves (this makes it difficult to cross without propulsion). Extremely large sea monsters called Sea Kings live in the Calm Belts; in fact, the monsters found in the Calm Belts are the largest shown thus far in all of One Piece. The combination of no currents, no wind, and the presence of the Sea Kings makes these belts perfect barriers to any traveler trying to directly go into the Grand World.
Without using Kairoseki-lined ships (which are concealed from the Sea Kings to a certain degree) and some propulsion, the Grand World can only be accessed at two points on the Red Line: Reverse Mountain and the Holy Land of Mariejois. The first is where the four major currents of the Blues merge together to form the Grand World, while the second is the site of the World Government.
The Grand World is divided by the Red Line into two halves. The first half, stretching from Reverse Mountain to the polar opposite point of the Red Line, is known as "Paradise". The second half, which starts beyond the second Red Line point to the backside of Reverse Mountain, is known as the "New World".
The first half of the Grand World is known as Paradise (楽園（パラダイス） Paradaisu) to those who have been to the New World. It lies between East Blue and South Blue. While the Grand World is a dangerous place, the first half is known as such in comparison to the more terrifying dangers present in the New World.
The New World (新世界 Shinsekai) is the second half of the Grand World. It lies between North Blue and West Blue. This half has not been fully explored. This area is also where the Yonko reign.