The man was found lying near a pedestrian and bicycle path between Anderstorp and Gislaved in Småland.
The man was taken to hospital with life-threatening injuries where he underwent surgery overnight.
Police have classified the incident as attempted murder.
“A witness passing by came across the man and called emergency services,” Bengt Netterström, duty officer with the Jönköping County police, told the TT news agency.
Police have searched the area with dogs and cordoned off an area near where the man was found to carry out a forensic investigation.
As of early Wednesday morning, no arrests had been made.
The injured man was discovered in a deserted area around midnight.
He was first taken to hospital in Värnamo before being flown by helicopter to Sahlgrenska hospital in Gothenburg for surgery, according to TV4 news.
Police elected not to release any additional information about the man’s injuries or about a possible motive.
“According to my assessment, (the injuries) are life threatening. He’s in surgery at the moment,” Netterström told TT at 2am on Wednesday morning.