About 8,000 people in Wales go into cardiac arrest outside of hospital every year.
The Welsh Ambulance Service says every minute without using a defibrillator cuts the chance of survival by 10%.
The campaign is being launched on Wednesday, backed by rugby legend Shane Williams and footballer Lee Trundle.
"I never fully understood how important it is knowing where your nearest defibrillator is. It literally saves lives," said former Wales international and all-time leading try scorer Williams.
Dr Brendan Lloyd, Medical Director for the Welsh Ambulance Service, said: "When someone goes into cardiac arrest, early defibrillation is a crucial part of the chain of survival.
"In fact there are a number of people in Wales who are alive today thanks to the quick-thinking actions of bystanders in using a nearby defibrillator.
"That's why we're encouraging everyone to familiarise themselves with where they can find the closest piece of lifesaving equipment available to them."
As well as taking photographs, people are being urged to share them on social media, with prizes on offer for posts on Twitter, including two defibrillators for schools - and tickets for the Wales football World Cup qualifier against Austria.
"Hopefully you will never need to use it, but it really could make all the difference," added Dr Lloyd.
People are being urged to take selfie photos next to defibrillator machines, so they know where the equipment is to help save lives.