Lady Chryss O'Reilly, who owned the famous Castlemartin Stud in Co Kildare along with her husband Sir Anthony O'Reilly, has died aged 73. 

Lady O'Reilly died unexpectedly at her home in Normandy, France on August 23, according to the Irish Times.

Born Chryssanthie Goulandris to Greek shipping tycoons in the US in 1950, Lady O'Reilly went on to become a legend in Irish horseracing circles and was the former chairperson of the Irish National Stud.

She co-owned Castlemartin Stud in Co Kildare with her husband Sir Anthony 'Tony' O'Reilly.

"Lady O’Reilly has been involved in racing and breeding since the 1970s," Castlemartin Stud's website says, "enjoying significant success as an owner and breeder both in Ireland and France.

"At the turn of the century, her broodmare band numbered 125. Successful products of Lady Reilly’s breeding programme include over 20 Group 1 winners including Bluemamba, Equiano, Helissio, Hoghest Honor, Priolo and Shaka.

"On the home front, Chryss O’Reilly has won the Irish St Leger with Voleuse De Coeurs, the Pretty Polly Stakes with Chinese White, and the Tattersalls Gold Cup with Rebelline. Verglas, a winner for her at Royal Ascot, subsequently stood at the Irish National Stud, of which Chryss became a long-serving chairperson from 1997.

"Thanks to the O’Reillys. Castlemartin has become a national treasure and its future is safe in the hands of John and Leslie Malone, who have invested significantly in upgrades throughout the farm."

Chryss and Tony first met in New York in 1989 and met again the following year at a race in Ireland. They got married in the Bahamas in 1991.

In April 1996, Tony O'Reilly paid more than $2.5 million for a 40-carat diamond engagement ring that once belonged to Jacqueline Kennedy Onassis

Lady Chryss was also a director at the Ireland Funds, which her husband cofounded in the mid-1970s, and was the first chair of the Barretstown Castle children's charity, to which she donated about €1 million of her own funds

The Irish Times reports that Caitríona Fottrell, president and chief executive of the Ireland Funds, paid tribute to Lady O'Reilly, saying "her broad support of culture and the arts in Ireland as well as her generous support of our Pittsburgh Dinner (where the O’Reillys were based during his time as chief executive and chairman of HJ Heinz), were just some of her many philanthropic contributions to the work of The Ireland Funds.

"We are forever grateful for her involvement.”

Irish trainer Eddie Lynam also paid tribute to Lady O'Reilly, describing her as a "very kind woman."

"I was fortunate to have trained for her for 15 years, maybe more, and she was a pleasure to train for, as she was very knowledgeable. She will be sadly missed in racing throughout the world," Lynam said. 

Lady O'Reilly was a popular figure in the horseracing world and was seen at a horse sale and racing event in Deauville earlier this week.