You are not permitted to download, save or email this image. Visit image gallery to purchase the image.
The Cliffsofmoher, prepared by master trainer Aidan O'Brien, pulled up lame early in the gruelling 3200-metre handicap won by Cross Counter, and was later put down on the track after vets found the five-year-old stallion had broken a shoulder.
"Unfortunately, these things can happen to a horse galloping around the field at home," Irishman O’Brien said.
"It’s very sad. It could have been worse, (jockey) Ryan (Moore) could have taken a fall off him, someone could have been seriously injured."
Melbourne Cup day has proved a lethal undertaking for runners in recent years, with six horses killed after complications since 2013.
Regal Monarch, trained by Chris Waller, was euthanised after falling in race four last year, while British stayer Red Cadeaux was put down two weeks after falling and breaking a leg in the 2015 Melbourne Cup.
The 2014 race claimed the lives of two runners in favourite Admire Rakti and seventh-placed Araldo, while French mare Verema died after breaking her leg in the back straight of the 2013 edition.
"The CliffsofMoher had won $1.7 million dollars for his owners," animal rights group Animals Australia wrote on Twitter.
"Today, he broke his shoulder during the 2018 #MelbourneCup & died on track behind the notorious 'green screen of death'.
"Animals & #gambling money are a TOXIC mix. Another beautiful horse dead. He deserved better."
Racing Victoria, the governing body in Australia's southern state, said The Cliffsofmoher "was unable to be saved due to the nature of the injury sustained".
"This was an unfortunate incident that happens infrequently, with Victoria having one of the best safety records in world racing," Jamie Stier, Racing Victoria's manager of integrity services, said in a statement.
"Our sympathies are extended to Coolmore and the Williams family, the owners of The Cliffsofmoher, jockey Ryan Moore, trainer Aidan O’Brien and his staff who cared for the horse and are greatly saddened by their loss."