Roy Mustang (ロイ・マスタング Roi Masutangu) is a character from the Fullmetal Alchemist anime and manga series. Holding the title of the Flame Alchemist, he is a skilled State Alchemist who ambitiously strives to become the next leader of Amestris. Although he has also held the ranks of Major (in flashbacks), Lt. Colonel (episodes 3-8), Brigadier General (episodes 45-51), and Corporal (The Conqueror of Shamballa movie after resigning his commission), Mustang holds the rank of Colonel in most of the anime and manga, and so he is referred to as such here.

Source: Wikipedia