Poison is a status in Final Fantasy VIII. When an afflicted combatant takes an action, they take damage equal to 5 to 7% of their maximum HP. The damage is non-elemental, thus even if the player junctions the afflicted to absorb Poison damage, they still take damage. The effect remains indefinitely until healed, even outside of battle. The afflicted has green bubbles above their head. Poison status is effectively the opposite of Regen in many ways, but the two are not mutually exclusive.
Poison can be used offensively to deal some damage whenever the afflicted acts in battle, but the damage is fairly minor and most bosses are immune. It can be good bonus when using abilities that inflict multiple ailments at once, such as ailment-inducing Limit Breaks and even Pain, but enemies that are vulnerable to statuses are best inflicted with ailments that disable them or instantly defeat them.