The Ireland-born jockey rode 4,632 winners before his retirement in 2003 including 14 British classics.
Only Gordon Richards (4,870) has ridden more winners in Britain than Eddery who had been suffering from ill health.
Five-times champion jockey Willie Carson said he was devastated to learn of the death of his friend.
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"He was a huge part of my life because we were together and friends for a very long time," Carson told At The Races television on Tuesday.
"An absolute gentleman, one of the greatest jockeys ever to ride a horse. Part of my life has gone as well.
"When he retired he hit a problem because racing had been his life, all he ever wanted to be was a jockey. He tried the breeding game which didn't work, he never settled into retirement," added Carson.
"Pat always had the knack. When he was on a horse he always did the right thing and got horses running for him."
Eddery's successes included Epsom Derby victories with Grundy in 1975, Golden Fleece in 1982 and Quest For Fame in 1990.
However, his display aboard Dancing Brave in the 1986 Prix de L'Arc de Triomphe in one of the best fields assembled was one of the most memorable of his career.
Eddery rode seven winners in a day on June 26, 1992, three at Newmarket and four at Newcastle.
Twenty-times champion jump jockey Tony McCoy described him as a "true genius in the saddle".
(Writing by Tony Jimenez; Editing by Justin Palmer)
