During the run of the series and her life as a Charmed One, Piper is shown to have clinically "died" 9 times. These are her deaths:
Deja Vu All Over Again
Killed by an energy ball thrown by demon Rodriguez after time was reset.
Killed by a terminal illness but Leo healed her at the last minute.
Killed by Prue in order to get a spirit out of her body -An alchemist revived her.
All Hell Breaks Loose
Killed by a crazy Wiccan practitioner, because she thought Piper was evil,After time was reset.
Saving Private Leo
Killed(stabbed) by Leo's ex-army mates and turned into a spirit. Leo came to her side to heal her just in time.
I Dream Of Phoebe
An evil Genie wished for her death.Leo, while sleeping, healed her before she could cross over.
Styx Feet Under
The Angel of Death killed her and gave her the job of collecting souls. The Angel of Death returned to doing his job.
Someone To Witch Over Me
Killed by a celerity demon.Leo brought her and Phoebe back to life after becoming an avatar.
[b]The Seven Year Witch
She had to die in order to reach out to Leo. Wyatt healed her at Drake's request.