Aidan O'Brien Will Enter Three Horses for Arc
The trainer prepares his Ballydoyle stable for the October 4, 2026, race at ParisLongchamp.
Updated on Sept. 28, 2026 in Equestrian
Trainer Aidan O'Brien will field three horses in the upcoming Prix de l'Arc de Triomphe on October 4, 2026. The Ballydoyle challenge is expected to be led by Diamond Necklace as the group heads to ParisLongchamp.
Why it matters
The race serves as a marquee international event that pits elite European thoroughbreds against each other at one of the world's most prestigious tracks. Success at the Arc remains a defining goal for top stables looking to cement their status in the sport.
Diamond Necklace enters with four Group One wins to her name. She is now preparing to race over a mile and a half for the first time, extending her reach beyond the mile and 2 furlong distance seen at the Prix Jean et Louis Romanet.
The players
Aidan O'Brien
He is a prominent Irish thoroughbred horse trainer who oversees the Ballydoyle stable.
Diamond Necklace
She is a highly accomplished filly whose previous victories include the French Guineas, French Oaks, and the Nassau Stakes.
Ryan Moore
He is a world-class jockey who serves as the primary rider for the Ballydoyle stable.
The details
Diamond Necklace, Minnie Hauk, and Benvenuto Cellini comprise the trio currently being readied for the international stage. While Diamond Necklace is the primary prospect, connections have noted she could alternatively contest the Prix de l'Opera, a race that may also feature Precise.
Timeline
The Prix de l'Arc de Triomphe is scheduled for October 4, 2026.
Season Trajectory
Participation in the Prix de l'Arc de Triomphe represents the pinnacle of the European middle-distance turf season. This race acts as the ultimate benchmark that determines end-of-year championship standings for top horses and stables alike.
A potential shift for Diamond Necklace toward the Prix de l'Opera would significantly alter the depth of the field in both events. Jockeys and betting markets remain in flux until Ryan Moore makes his final selection for the ride.
The takeaway
The Arc attracts the strongest field of international competitors in the sport each year. Followers of major racing should monitor final declaration lists to see which horses bypass the main event for alternative stakes races.
Further reading
For more news on upcoming international events, visit Equestrian.
