Ian Olding and Gran-Kiki © British Eventing
Olding, 47, from County Antrim, was competing in the advanced class when his horse Gran-Kiki fell on him while negotiating fence 13a, a square spread fence. An investigation into the accident is now under way.
The event was held up for two hours, after which organisers decided to continue the competition.
Eventing Ireland Chairman John Wright said from Dublin: "We are shocked at this sad fatality and on behalf of Eventing Ireland I would like to express our deepest sympathy to Ian's family, friends and colleagues and also to our colleagues in British Eventing. Ian was well known and well liked on the international circuit, where he rode for many years. He moved to Cheshire ten years ago to live and work. Everyone here is very saddened by this tragic event."
Olding was based in Sandbach in Cheshire. Gran-Tiki, a 12-year-old with 114 BE points, is owned by Olding and Mrs Sue Kirkpatrick.
"Our sympathies on this sad day are with Ian's family," said Mrs Alex Fox, Chairman of British Eventing. "Ian was a well-known and much respected rider, who has been competing for many years. Our thoughts are with his family and friends."