A teenage girl has died at a horse eventing championship in the Upper Hunter Valley.

The 17-year-old girl, named by Equestrian Australia as Olivia Inglis, was competing at the trials near Scone.

It is understood she died when her horse got into trouble during a combination jump and flipped.

The event was subsequently cancelled.

Organised by the Hunter Thoroughbreds Association, the championships were scheduled for this weekend at the Broomfield ground outside Gundy.

Equestrian Australia said Ms Inglis was riding the family horse in the event's competition about 9:20am when the accident happened, about 2 kilometres from Scone.

Ms Inglis was treated by staff on the course and medical crew from the Westpac rescue helicopter but died at the scene.

Chair of Equestrian Australia Judy Fasher described the accident as "absolutely horrendous".

"This is exactly what we dread in eventing. It is an awful thing to happen," she said.

"This was absolutely something that we couldn't have predicted.

Olivia Inglis was killed in a horse eventing accident near Scone on Sunday morning. ( Facebook )

"The fence had actually been jumped by three other riders before Olivia was present at the fence and there had been no problems at that fence.

"It is also a fence that was used in the same course last year.

"But just occasionally horses make a mistake ... [and] when they do it can be catastrophic."

Olivia is the daughter of Charlotte and Arthur Inglis.

The Inglis family are well known in the world of horseracing and breeding, operating the leading bloodstock company which carries their name.

Equestrian Australia said counselling services had been arranged for event attendees.

Eventing is a discipline which involves dressage, cross country and show jumping.