The four-yearly event is taking place in Tryon, North Carolina, USA.
Competition is underway at the FEI World Equestrian Games in the United States.
The event, which takes place every four years opposite to the Olympic Games, serves as the world championships for the world's top equestrian athletes.
But this year's schedule is under threat, as a major storm, Hurricane Florence, is forecast to affect the host state of North Carolina.
Here's everything else you need to know about the Games, which last until 23 September.
11 - 23 Sep 2018
FEI World Equestrian Games - Tryon
This year's World Equestrian Games are being held in Tyron, western North Carolina; population 1,700.
The FEI expect 500,000 people to attend, nearly 300 times the town's size.
There are competitions planned in eight disciplines for the next 12 days, although the impact of storm Florence may result in changes.
The opening ceremony went ahead without disruption.
Athletes from over 70 countries are taking part in Tryon, while their equine counterparts come from all six inhabited continents on Earth.
The horses will stay in 1,200 stalls across seven barns at the host venue, the Tryon International Equestrian Center.
Many of the world's top riders have turned up at the Games, which also double as an Olympic qualifier for Tokyo 2020.
Olympic spots are available for teams in the disciplines of dressage, eventing, and jumping,
There are also events being held in driving, endurance, reining, vaulting, and para-dressage.
The world's biggest names will be in Tryon, ranging from Olympic champions to national leaders.
Two-time Olympic individual champion Charlotte Dujardin rides Mount Saint John Freestyle in the dressage competitions, while five-time Olympic team champion Isabell Werth (on Bella Rose) is part of a strong German team hoping to defend their WEG title.
Equestrian legend Mark Todd is part of the New Zealand eventing squad, 28 years after his appearance in the inaugural World Equestrian Games. The Kiwi has won two Olympic golds, at LA 1984 and Seoul 1988. Defending champion Sandra Auffarth will aim to retain her title, having been called in as a late replacement by Germany for hot favourite Michael Jung whose horse is injured.
Jumping competitions are scheduled to begin next Wednesday, 19 September. Rio 2016 Olympic champion Nick Skelton has retired, leaving silver medallist Peder Fredricson of Sweden as one of the favourites. World number one Harrie Smolders is also expected to do well while leading the defending team champions Netherlands.
Sheikh Mohammed Rashid al-Maktoum, the ruler of Dubai and 2012 world champion, is competing in the endurance (120 km long-distance) event, as is his son and Crown Prince of Dubai, Sheikh Hamdan Mohammed al-Maktoum.