Noctis Lucis Caelum (Tatsuhisa Suzuki)
Prince of the Lucis Kingdom, possessing eyes which can sense the death of others. His close friends call him Noct.
Gladiolus Amicitia (Kenta Miyake)
The eldest son of a household tasked with protecting the royal family from generation to generation. A close friend of Noctis who is closer to him than a true brother.
Ignis Scientia (Mamoru Miyano)
A childhood friend of Noctis who grew up recieving gifted education befitting a staff officer. He understands Noctis well and is his confidant.
Prompto Argentum (Tetsuya Kakihara)
A friend who has been a bad influence to Noctis since his school days. While he can get carried away easily, there's another side of him which is driven to help friends in need.
Cor Leonis (Hiroki Touchi)
Head of Royal Family Guards, and one of the three strongest fighters in Lucis. While he is harsh to Noctis and the others, he is a true man of honor who takes his vows to king and country very seriously.
The characters are also the ones on the key visual poster they showed at the Future of FF media briefing. From left to right it's Prompto, Gladiolus, Noctis, Ignis, and Cor: