The legendary Australian racehorse Black Caviar, who captured the hearts of Australians with his unbeaten series of 25 victories, has died one day before his 18th birthday.

Black Caviar’s trainer Peter Moody hailed his famous mare as “a remarkable horse who gave us all the ride of a lifetime and wonderful memories,” while the champion’s ownership group said: “Black Caviar was a once-in-a-lifetime horse, most famous for her outstanding racing career in which she remained unbeaten with 25 wins from 25 starts.”

“The ownership group is devastated but will remember her brilliant achievements, not only in Australia, where she transcended racing to capture the hearts of the public, but also in England, where she won the Group 1 Diamond Jubilee Stakes (1200m) at Royal Ascot in 2012.”

With her distinctive salmon pink and black-spotted colours, Black Caviar became a national heroine. Australia was fascinated by the story of how unconventional trainer Peter Moody, a self-made man from the Queensland outback, paid just $210,000 for her in 2008 and then transformed the stocky, injury-prone mare into a champion.

At the height of her fame, when she equalled the legendary Phar Lap’s streak of 14 consecutive wins set 80 years earlier, Black Caviar was celebrated worldwide as the “fastest horse in the world”.

Trained by Moody and ridden by jockey Luke Nolen, Black Caviar has amassed nearly $8 million in prize money. She was the world’s top sprinter for four consecutive years from 2010 to 2013 and was inducted into the Australian Racing Hall of Fame in 2013, the same year she retired from racing.

Moody confirmed Saturday that Black Caviar had been humanely euthanized that morning at Scone Equine Hospital after giving birth to a foal. “You don’t think it affects you,” Moody told reporters in Caulfield. “But you’re stupid if you don’t think it doesn’t. It’s impossible not to get attached to most animals, let alone one like her.”

The Victoria Racing Club also paid tribute to her. “Today’s news comes as a shock to us all,” chairman Neil Wilson said in a statement. “Black Caviar was more than a champion racehorse, she was an important part of many people’s lives.”

“Her genius, her presence and the joy and inspiration she brought to so many people was a special moment for horse racing and sport in general. She created a piece of history that will be remembered forever and it was a privilege for all who saw this wonderful equestrian in action.

“It was an honour for the VRC to have Black Caviar race at Flemington and to name the 2013 Lightning Stakes after her. She won the race three times, including the first year it was named in her honour.

“Our deepest condolences go out to her family, including our friends in the ownership group. To Black Caviar’s trainer Peter Moody and jockey Luke Nolen: Our thoughts are with you on this sad day.

“She was simply the best.”