Conchita Wurst stole the show at Europe's biggest charity event, despite plenty of big-name competition.

Party-goers dressed in little more than body paint rubbed shoulders with men in tuxedoes and cross-dressers in wild costumes, transforming Vienna's City Hall into a fantasy land.

The occasion, Europe's biggest charity event, was serious - raising money for AIDS research.

But as in previous years, the 20th annual Life Ball was also an anything-goes gala with an emphasis on diversity.

Wurst, who won the recent Eurovision song contest, was the undisputed favourite.

Hoots of approval, applause and whistles greeted the bearded drag queen dressed in figure-hugging silver lame, as she belted out her winning torch song Fly Like A Phoenix.

Minutes later, formally clad VIP guests holding 750-euro tickets began streaming inside the neo-gothic hall for a night of food, dancing and champagne-filled revelry.

But there was plenty of big-name competition.

"I feel so poorly dressed," quipped a black-suited Bill Clinton, glancing down from the stage at the feather boas, fantastic head-dresses and exotic outfits among the 4,000 or so ball goers.

The former president urged all attending not to forget what lies behind "all the joy of this evening: the determination of every person ... here to give every child a better chance".

Other well-known attendees included Ricky Martin and Desperate Housewife Marcia Cross, who co-presented an award to SWAP, a Kenya-based charity working to provide clean water to AIDS victims.

"I'm wearing McQueen because I knew I couldn't compete with the beauty and extravagance around here," Cross said of her flowered outfit from the British design house.

"So I thought I would just be a delicate flower in this extraordinary garden."

This year's theme was "Garden of Delights," after the painting of similar name by Hieronymus Bosch.

Male models accompanied by statuesque women strutted their stuff, showing off tuxedos by Jean Paul Gaultier, Vivienne Westwood and Lanvin, among others.

But the real eye-catchers were the costumed party-goers - Arabian sheiks, rococo queens of all sexes, men in Carmen Miranda headgear and others in outfits that defied classification.

Jeans or cut-offs were verboten, and style police were present to enforce the dress code.

While Wurst came and went within a few minutes, some of the other big names remained star-struck by her aura.

"Conchita is unique, fantastic, the best," exulted Gaultier.

"This styling! I love her!"