Australia's Sara Carrigan has upstaged the favourites to win the Olympic women's road race in Athens.

Carrigan, 23, took off with about 10km left in the 118.8km race but was quickly caught by Germany's Judith Arndt.

The pair then waged a gripping battle in the closing stages until the 23-year-old from Queensland accelerated 100 metres from the finish.

Arndt, Germany's world No. 2, took the silver with Russian Olga Slyusareva just pipping Australian Oenone Wood for the bronze.

Wood was expected to be Australia's main hope in the nine lap race around the scenic hills and antiquities of Athens, but after a discussion between the two teammates early in the final lap, Carrigan went for it.

Canada's Susan Palmer-Komar had led by 52 seconds in the eighth lap but was chased down by Wood and, at the bell, the Australian pair was among a group of nine riders in the lead.

They spoke briefly with 10km to go and a minute later the Gunnedah-born Carrigan, who was a reserve at the Sydney Olympics, took off with the gold medal in her sights.

Dutch world No. 1 Mirjam Melchers faded to sixth, while Sydney Olympic champion Leontien Zijlaard-van Moorsel, also of the Netherlands, crashed out with two laps to go.

She staggered to the side of the road clutching her head and needed medical attention but was not thought to be seriously injured.

France's former Olympic champion Jeannie Longo-Ciprelli, competing at her sixth Games at the age of 45, never figured among the leaders but finished in the pack.

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