From A Wiki of Ice and Fire
King-beyond-the-Wall is the name given to a person who has united the many tribes of Free Folk or wildlings under his authority. The term seems to have been invented by the people of the Seven Kingdoms. Despite its name, the title is not necessarily a hereditary or absolute position. It is not a position of any authority except that of the person who can establish it through persuasion and force. For long periods of time there can be no recognized king. The most recent King-beyond-the-Wall, Mance Rayder, competed against multiple other contenders, bribing and bargaining with the many tribes to recognize him as their leader.
- Raymun Redbeard. He was king some 150 years ago.
- Bael the Bard. Bael was a famous bard, raider and womanizer. According to the wildlings he went to Winterfell as a bard and impregnated the daughter of the lord. When he was king, he led the wildlings against the Wall, where he was killed by his own son, who had inherited Winterfell. Later, his son was skinned by the Boltons in their centuries-long struggle for dominance.
- Gendel and Gorne. The brothers Gendel and Gorne were joint kings some 3,000 years ago. They made a tunnel under the Wall and invaded the North. Gorne managed to slay the Stark king but was killed by his son and heir. According to the people of the North Gendel and the remaining wildling army were killed by the armies of the Starks, the Night's Watch and the Umbers. In the wildling stories, Gendel led his people back to the tunnels, but they could not find the exit. His children and descendents are said to still live underground, and are always hungry.
- The Horned Lord
- Joramun. A contemporary of the Night's King, the thirteenth Lord Commander of the Night's Watch. Together with the King of Winter they defeated the Night's King. Another story tells of how he found the Horn of Winter and woke the giants.
- Mance Rayder