Grand race mare Snow Fairy has been retired due to a recurring tendon injury.

Trainer Ed Dunlop called time on the six-time Group One winner's career after she suffered the injury during a workout on Tuesday morning (Wednesday AEST).

"It is with much sadness that a decision was made this morning to retire Snow Fairy," Dunlop said in a statement.

"Unfortunately after a routine piece of fast work today she was found to have re-injured her near fore tendon, which has caused her problems in the last two years."

Snow Fairy secured just under STG4 million ($A6.67 million) prize money in a career during which she won a number of the world's top races.

She was last seen claiming the Irish Champion Stakes at Leopardstown in September 2012.

Dunlop said Snow Fairy would now return to Ireland to begin a career as a brood mare.

"I would like to take this opportunity to personally thank Mrs (Cristina) Patino for all she has done. She has been the most wonderful owner of a truly amazing horse," he said.

"Most owners would have retired her a lot sooner than she did and if this had been the case she would not have won the Irish Champion Stakes last year, which was without doubt her greatest performance.

"She remains the only international horse to have won two Group Ones in Japan."

Although she showed form as a juvenile, it was as a three-year-old that Snow Fairy really made her mark.

After completing the English and Irish Oaks double, the filly capped off a momentous 2010 campaign with further Group One victories in Hong Kong and Japan.

Her 2011 return was delayed after she suffered the first of what became a string of injury setbacks, but she ended the year with another glorious display in Japan's Queen Elizabeth II Commemorative Cup.

Snow Fairy was stripped of her win in last August's Prix Jean Romanet at Deauville when a banned substance was found in a sample.

A sixth Group One victory was not far away, however, as she beat top-class colt Nathaniel in Leopardstown's Irish Champion Stakes.

In all, Snow Fairy won eight of her 21 career starts and was placed on a further eight occasions.