Cheltenham Gold Cup winner Burrough Hill Lad has been put down at the age of 28.
Burrough Hill Lad is led in after the 1984 Gold Cup
The Jenny Pitman-trained horse claimed the blue riband event in 1984.
He won half of his 42 races and was champion chaser for three seasons in the mid-1980s.
The gelding enjoyed 14 years of retirement at Frickley, near Doncaster, and was put down on Wednesday, the Racing Post reported.
Burrough Hill Lad featured at number 44 in a poll of the all-time 100 favourite racehorses being carried out by the newspaper.
Charlie Warde-Aldam, who looked after the horse, said: "The last few weeks, he had been a bit listless, he was down two or three days ago and not keen to get back up.
"Then he was down again this morning but could not get up, so we decided to put him out of his misery."
Phil Tuck rode Burrough Hill Lad to victory in the 1984 Gold Cup, after his usual partner John Francome chose to ride Brown Chamberlin, who finished second.
Burrough Hill Lad may have added to his Gold Cup win, but was withdrawn from two subsequent runnings with late injuries when ante-post favourite.
But victories in other top races, such as the Welsh National and Hennessy Cognac Gold Cup, took his career prize money to nearly £200,000.
He also won Sandown's Gainsborough (now the Agfa) Chase three times in succession.