Meliandre or Melisandre of Asshai is a shadowbinder from the distant country and city of Asshai, acting in the service of King Stannis Baratheon. She is also a priestess of the Lord of Light or Red God, R'hllor.
According to Melisandre, her ultimate goal is to ensure the victory of R'hllor over the Lord of Darkness and Cold, the Great Other, whose return will be heralded by a deep and lengthy winter. Melisandre has the ability to see visions of the future in fire, and concluded that Stannis Baratheon was Azhor Azhai reborn, the man prophesied to lead the victory over the Others in this war, and this would only be possible if he became King of Westeros. After Stannis' defeat at the Battle of the Blackwater, Melisandre claims to have arranged the deaths of Robb Stark, Joffrey Baratheon and Balon Greyjoy through her magic, although the truth of this is uncertain. When Davos Seaworth discovered a long-forgotten message from the Night's Watch begging for aid and warning of unusual events happening beyond the Wall, Melisandre realised this was the beginning of the true struggle and convinced Stannis to sail for the Wall with his remaining strength to prosecute the war from there.
Despite claiming benign motivations, Melisandre is viewed with suspicion from some, due to her extreme ruthlessness.
After laying out a series of clues for the identity of a previous unrevealed POV character in A Dance with Dragons, George R.R. Martin has revealed that Melisandre will indeed be a POV character in that book, with at least one chapter.