For three days, the open-air spectacle will entertain its audience with some 2,000 artists and more than 600 hours of programming.
Highlights include performances by Panda rapper Cro, Milow, Macy Gray, Picture Book and Adel Tawil.
On Sunday, Conchita Wurst will honour the island as a 'surprise guest', fresh from the London Pride festival.
Eleven stages and 19 theme 'islands' are planned for this year, ensuring there's something for every taste. Entrance is free.
Included in the entertainment will be a 20 meter long slackline, for those who want to test their balancing skills.
A full complement of police and paramedics will be on duty, to ensure the event is problem free. Experienced medics recommend that festival-goers drink moderately and stay hydrated with water, as the weather will be hot.
Also the European ideals of peace will not be neglected in the year of the World War One centenary - in addition to a peace message from Mayor Michael Häupl (SPÖ), the organizers plan to broadcast a portion of a memorial concert by the Vienna Philharmonic from Sarajevo.
How many people flock to the 6.5 km long island this year, remains to be seen. Last year the 30th anniversary festival set a new record of 3.2 million visitors.
By way of comparison, the nearest contenders for the world's biggest music festivals are Summerfest in Wisconsin, USA, and Mawazine in Morocco, which each have a million visitors in around ten days.