One of the best mares in Australia, Cox Plate winner Pinker Pinker, has died after reportedly suffering a reaction to a routine treatment.

Trained in Victoria by Greg Eurell, Pinker Pinker was due to contest the Group One Queen Of The Turf Stakes at Rosehill on Saturday.

The Eurell stable informed Sydney stewards on Wednesday afternoon of the mare's sudden death.

A four-year-old by Reset out of Miss Marion, Pinker Pinker cost $120,000 as a yearling.

She raced 18 times for six wins, none more spectacular than her success in last year's Cox Plate.

She was also Group One-placed in the 2011 Australian Oaks and banked more than $2.6 million prizemoney.

More Joyous is now an overwhelming favourite for the Queen Of The Turf Stakes.