Immunity

 is a Pokémon ability introduced in the third generation. It prevents poisoning.

Description
When a Pokémon with this ability would get poisoned, they do not. If the Pokémon got poisoned (either getting Poisoned before the ability was given to them or getting hit by a poison-afflicting move from a Pokémon with Mold Breaker), they get cured once their turn starts. The Pokémon consumes its Pecha Berry or other Poison-healing held item before Immunity activates.

From the fifth generation onwards as well as the third generation, if a poisoned Pokémon originally had Immunity but, currently does not, it will not heal its poison.

When outside of battle, if a Pokémon with this ability somehow got poisoned, they will not take poison damage. Battle Frontier events that poison won't poison this Pokémon.

Pokémon with Ability

 * Snorlax
 * Zangoose

As a Hidden Ability

 * Gligar

Trivia

 * Immunity works similar to Limber, Oblivious, Insomnia, Own Tempo, Inner Focus, Magma Armor, Water Veil and Vital Spirit in battle in that it prevents a certain status condition