The best Slovenian divers will be joined by colleagues from Serbia, though all eyes will be on Pino Auber, a 77-year-old who has become an icon of the event.
The divers jump into the emerald water from a wooden construction mounted on the picturesque bridge over the Soča.
Held since 1988, the event always attracts hundreds of spectators to the banks of the Soča, who will be treated to an array of events.
The diving will be the highlight, but there will also be an artisan market, a show of vintage cars, a running event, and a party in the evening with live music.
The current bridge was built after WWI, replacing a structure blown up by the Austrian army during the war.
But various bridging structures have spanned the narrow Soča there since Roman times.