Natasha Baker's horse Cabral, which she rode to three Paralympic Games gold medals in Rio de Janeiro, has died after contracting a bacterial infection.
The Briton won the individual championship test and individual freestyle test events in Grade II at Rio 2016 on board the horse, which was nicknamed "JP".
The 16-year-old horse died after suffering a small cut while grazing on Baker's farm.
Cabral then caught the Clostridia bacterial infection, which is common in horses and foals and can cause sudden death.
In a statement on her website, the 27-year-old, who also won two gold medals with the horse at the Paralympics in London in 2012, said: "I’m writing this with a totally broken heart.
"This weekend I suddenly lost my soul mate, my best friend and my dancing partner.
"After a short illness from a small wound from the field, JP contracted Clostridia bacteria.
"JP was a horse like no other, a true legend.
"He was discovered by fluke and I instantly knew he was ‘the one’.
"He made my dreams come true over and over again.
"We’ve had the best journey together and he has given me memories I will treasure forever.
"I cannot thank him enough."
Baker enjoyed a period of huge success while partnering with Cabral, whom she started working with back in 2009.
"JP gave me his heart and together we took on the world," she said.
"Eleven gold medals, Paralympic records, endless national and international titles, we defied the odds and he gave me absolutely everything he had.
"He had the kindest soul and his heart was made of gold."