Mortality

Mortality is a state of being in which life is limited. Almost beast and beings, both magic and none magic alike, are subject to mortality. Spirits, however, are not.

Mortality
Almost all creatures are mortal. There are few exeption, such as; Vampires, Zombies, Inferi, Dementors, Charmed Skeletons, Boggarts, Ghosts, and Poltergeists. Creatures such as these do not grow old because they are not truly alive. Apart from this, pretty much all beings are mortal. Being magical doesn't change the fact that you are mortal.

Immortality
Apart from spirits and Living Dead, there are very few immortals and ammortals in the world. Humans who (out of despiration to escape death) tried to achieve immortality, discovered it could only be achieved through Dark Magic. But that didn't stop them.

However, the only wizards to achieve immortality wereHerpo the Foul and Tom Riddle. They did this by creating Horcruxes. If horcruxes are sentient entities (a topic that is currently debated) then they are immortals. Nagini (a serpant used by Voldemort as a horcrux) is also immortal.