The Swedish Olympic Committee had struggled to find a suitable candidate since most of the team is still residing at the pre-Games camp in Fukuoka, news agency TT reports.
Olsson said he was lying in bed at his home in Monaco when he got the call.
“I asked if I could have some time to think about it and talk to my girlfriend, but there was really very little hesitation. There are few people who get to participate in something this big and it is an honour for me,” he told TT.
A recurring thigh injury put paid to Olsson’s hopes of defending his Olympic gold medal just weeks before the start of the Games.
“I had just hidden myself away in recent weeks and I was happy for the Olympics to pass by without my involvement, but this feels great,” he said.