A St John ambulance stolen overnight in rural South Canterbury has been found abandoned 50km away.

St John officials have described the theft as "reprehensible".

After a Geraldine St John's station crew finished their last job yesterday, they locked the ambulance into the station garage just after 6pm.

When ambulance officers went to the station this morning, they discovered the ambulance was stolen, along with a St John ambulance uniform.

The ambulance, fitted with a GPS unit, was later found abandoned inland from Cave, some 50km away.

"It is reprehensible that someone would steal an ambulance, limiting our ability to provide essential emergency care to the public," said St John Canterbury District operations manager Dion Rosario.

"We are currently relocating another ambulance for the Geraldine crew to use so this doesn't impact patient safety."

A 37-year-old man, from Timaru, has been charged with theft, police confirmed this morning.

​