Gluttony (グラト二ー, Guratonī) is one of the first homunculi to appear in the series, typically being in the company of Lust. He is a large, simple-minded homunculus whose thoughts rarely stray far from eating. He has powerful jaws, acidic saliva, and can and will eat almost anything. He particularly likes eating people, and the only way he can find enjoyment in a battle is if he can eat his opponent afterwards.

In the manga, Gluttony is the failed product of Father's attempts to create a Gate of Truth. When activating this gate Gluttony's stomach opens up, revealing a large eye at its center. His ribs spread out to act as a border for the gate, and then double as large extendable teeth that can consume everything in his eye's field of vision in an instant. Anything Gluttony consumes is transported to a realm within himself, which is littered with artifacts from centuries before the start of the series. Gluttony tries to use this form to kill Roy Mustang, Lust's killer, though he makes the mistake of eating Edward Elric and Envy instead. After Ed and Envy manage to escape, the energy in Gluttony's Philosopher's Stone is exhausted in the ensuing battle, leaving him unable to revive himself. Father later restores him and sends him and Pride to capture Ed. When his Philosopher's Stone once again reaches depletion in the attempt, Pride consumes Gluttony to gain his abilities, and he dies thinking of Lust.

In the anime, after Lust's death, Dante transforms Gluttony into a mindless eating machine to stop his incessant crying, an act that ultimately backfires when he eats her. He appears again in Conqueror of Shamballa, having transformed into a large, multi-limbed monster since his appearance in the anime. He exclusively attacks Wrath (Lust's killer) during the movie, giving Alphonse Elric an easy opportunity to use Gluttony to create a gate to the other world.

Source: Wikipedia