Doriath is a forest realm of the Sindar in Beleriand ruled by King Thingol and his queen Melian. It serves as a principal stage for the stories of the First Age, such as The Tale of Beren and Lúthien from The Lays of Beleriand, and parts of The Children of Húrin and The Silmarillion. It is called the “Fenced Land” because of a girdle of enchantment Melian put about it, allowing none to enter the kingdom without her leave or Thingol’s.

Source: Doriath – Wikipedia