Jockey Pat Smullen, who rode 12 Classic winners and won the Epsom Derby four years ago, has died aged 43 from cancer.
The nine-time Irish champion was diagnosed with pancreatic cancer in 2018 and passed away in Dublin on Tuesday.
Smullen retired from racing in 2019, but he helped raise awareness with charity races while suffering from the illness.
More than €2.5m was raised for Cancer Trials Ireland last year when Smullen organised a race during the Longines Irish Champions Weekend at the Curragh.
The one-mile event captured huge attention and was won by Sir Anthony McCoy riding Quizical for Smullen's good friends Sheila and John Lavery.
"We can be very proud of horse racing in general in Ireland. The stable staff, racegoers, owners, trainers, jockeys - everyone has given so much support to the amazing man that Pat Smullen is," McCoy said back in September 2019.
McCoy added at the time. "Pat is a special person and a great friend to us all. Unfortunately it's tough and sad circumstances what we're doing today, but it just shows you what a brilliant sport this is."
Smullen was a multiple Group One-winning jockey around the world, and rode Harzand to four victories including the Irish Derby and Epsom Derby four years ago.
At Epsom Harzand - trained by Dermot Weld - was a 13-2 shot, and held off favourite US Army Ranger to win by one-and-a-half lengths.
Brian Kavanagh, chief executive of Horse Racing Ireland, told the PA news agency: "Pat was one of our greatest stars. He was nine-times champion jockey, but in many ways his greatest achievements were out of the saddle.
"Since his diagnosis, he did wonderful work fund-raising for charity and he battled this disease with great heart and it's hard to believe he has passed at such a young age. All our thoughts are with Frances and his three children, Hannah, Paddy and Sarah, and all his friends and colleagues in the weighing room.
"It's a really sad day for Irish racing. Pat was one of the finest men you could hope to meet. There's been such a reaction around Irish racing and such a degree of shock, which shows the high regard in which Pat was held.
"He was a pleasure to have anything to do with - his achievements in the saddle were one thing, but his qualities outside of it were something else.
"He was a global figure in racing, but his reaction to his diagnosis and the fund-raising he did last year in particular was really wonderful. It's just a sad, sad day."