The Dothraki Sea or Great Grass Sea is a region on the continent of Essos, thousands of miles to the east of Westeros. It is located in the continental interior, east of the Free Cities, and is a vast landscape of steppes and plains covered in low green grass which makes it look like a sea from afar. It is named for the Dothraki people who inhabit it, horse-mounted warriors who migrate across the plains in large hordes called khalasars (each of which may contain thousands of riders) to plunder neighboring lands. Vaes Dothrak, the only city of the Dothraki and central hub of their society, lies on the northeastern edge of the Dothraki Sea. The Dothraki Sea lies north of Lhazar, Slaver's Bay, and the forbidding Red Waste, which even the Dothraki fear to cross. The southern border is loosely marked by the Skahazadhan river. The Red Waste protects the city of Qarth from Dothraki attack. The Dothraki sea stretches almost all the way to the Jade Sea, but stops short due to intervening mountains and forests. However, the Dothraki still occasionally raid the rich cities of the western Jade Sea for treasure and slaves. The Dothraki Sea borders the Forest of Qohor to the west, separating it from the Free Cities. However the forest does not present a significant obstacle to their hordes, which frequently threaten the Free Cities with raids or to exact tribute.

The Dothraki Sea has actually been home to a number of advanced cultures throughout history, such as the Kingdom of Sarnor, which held sway during the rise and reign of Valyria. The region was actually heavily developed and urbanized for much of the time following the Long Night. During the Century of Blood, the Dothraki grew in strength, and were used by the Sarnori in their petty wars against each other. By the time they realized the true threat, it was too late, and the Dothraki eventually destroyed all the Sarnori cities, including the library city of Sallosh, which contained records of the Sarnori and all the cultures they had conquered and assimilated over the centuries. The Dothraki also destroyed Essaria, the Ibbenese colonies on the north coast of Essos, and the few Qaathi holdouts that had not been swallowed by the Red Waste. Thus the entire region, not simply the grasslands of Sarnor, became the haunt of the Dothraki, and is in fact dotted with the slowly overtaken ruins of the cities that came before. Although the western and southern boundaries of the Dothraki sea are somewhat fluid, the eastern boundary is firm, as the grasslands come to a complete stop at the Bone Mountains, which the Dothraki for the most part cannot cross.

Notable places shown in the series are: