Australia's Jodie Henry smashed the world 100m freestyle record in a semi-final at the Athens Olympics.

Henry clocked 53.52s to slash 0.14s off teammate Libby Lenton's former mark, set four months ago at the Australian Olympic trials in Sydney.

Lenton failed to make the Athens final, clocking 55.17s in the opening semi - more than 1.5s slower than her March world record of 53.66s.

While Lenton left the pooldeck with a look of disappointment, Henry beamed after her world record swim.

"I'm just surprised by that time, that was awesome," she told Channel Seven.

She finished almost a body length ahead of the field in her semi-final, which included Dutch defending champion Inge de Bruijn and world champion Hanna-Maria Seppala.

De Bruijn hugged Henry after the race.

The 20-year-old Henry has had the quietest of Olympic buildups, allowing Lenton to hog the limelight pre-Games.

Her coach Shannon Rollason has deliberately kept her under wraps to keep her as relaxed as possible for her bid to become the first Australian woman since Dawn Fraser at the 1964 Tokyo Games to win the 100m freestyle.

The tactic obviously worked.

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