Green Moon thundered down the straight to win the Melbourne Cup on Tuesday, upsetting a host of highly fancied foreign horses to bring Australia's most coveted racing prize back home.

The Robert Hickmott-trained stallion charged to the front 300 metres from the line and held off fast-finishing Fiorente to win the punishing $6.43 million two-mile handicap by a length.

The Irish-bred six-year-old defied 22-1 odds and several quality European stayers to hand local jockey Brett Prebble his first Cup and owner Lloyd Williams his fourth.

Third-placed Jakkalberry finished a further length-and-a-quarter back.

Clad in blue and white silks, the Hong Kong-based Prebble punched the air in celebration as a packed crowd at Flemington Racecourse roared under leaden skies.

Prebble shook hands with Britain's Prince Charles in the crowd and said he knew the race was won at the 1,200 metre mark.

"It's a lifelong dream," Prebble told reporters.

"I thought the only thing that could get him beaten was his stamina if he didn't stay the trip.

"But the feeling he was giving me at the 1,200 was the sort of feeling you only get from very good horses.

"I've been very fortunate to ride some champions and he's up there in the top 10."

Last year's winner Dunaden and fellow French stayer Americain, who won the 2010 race, were favourites in the lead-up but failed to mount a serious challenge.

The Mikel Delzangles-trained Dunaden started favourite despite carrying the top weight of 59 kilogrammes but finished 14th in the 24-entrant field, while Americain ran in 11th.