100,000 spectators, a ready-made 2.3km racing arena and more than 1,700 runners decked out in matching underwear, the Undies Run is surely the most fun anyone can have in their undies.

Each year, hundreds of South Australians strip off before the People’s Choice Classic opening race of the Santos Tour Down Under cycling event in Adelaide running, jogging and strolling in their smalls to raise big bucks to help beat Australia’s second most-commonly diagnosed cancer.

Since its inception, the Undies Run has raised more than $600,000 for Cancer Council SA and has funded ground-breaking research and vital support services, while raising awareness of life-saving early detection bowel screening kits.

Registrations are now open online at undiesrun.com.au