The US horse Barbaro, who broke his leg in a race shortly after a stunning victory at the Kentucky Derby last May, has been put down.
Barbaro's recovery from injury had caught the attention of many
The four-year-old colt shattered his right hind leg in the Preakness Stakes and underwent a series of operations.
But he suffered more complications to the injury over the weekend which needed further surgery.
"We reached a point where it would be difficult for him to go on without pain," said co-owner Roy Jackson.
"It was the right decision, the right thing to do. We said all along if there was a situation where it would become more difficult for him then it would be time."
Barbaro won four of his five career starts and over $1m in prize money.
He first caught the public imagination by winning the Kentucky Derby by nearly seven lengths - the biggest margin in 60 years.
When he broke his leg two weeks later, more than $1m was raised for a fund in his honour and even Christmas songs were written about him.