Dean Holland, a South Australian-born 34-year-old, fell from Headingley at Donald Racecourse about 1.30pm on Monday.
He was treated by paramedics but died at the scene, Victoria Police confirmed.
A second jockey, Alana Kelly, also went down while riding Time To Rumble but was cleared of serious injury, Racing Victoria said.
Both horses were unharmed.
Holland, a well-liked and hard-working member of Victoria's riding ranks, had four young children with his wife Lucy.
His death comes a little more than a month after his latest career highlight.
Holland rode the filly In Secret to victory in the Group 1 Newmarket Handicap at Flemington on March 11, having only picked up the ride after fellow rider Jamie Kah was injured in a race fall earlier that afternoon.
It was his second and most prestigious top-tier victory, the first happening 13 years earlier in Adelaide.
Holland scored 1080 race wins throughout his career and had been riding in career-best form.
His total of 84 winners in 2022-23 was already one more than his previous high for a full season, with more than three months of the current term left.
"It was a tragic accident at Donald today and we are all deeply shocked and saddened that Dean has passed away as a result of injuries sustained in the fall," Racing Victoria CEO Andrew Jones said in a statement.
Holland's death was heartbreaking for all within racing in Victoria and Australia, and a sobering reminder of the bravery of riders, Mr Jones added.
Victorian Jockeys Association CEO Matt Hyland said it would do everything to make sure Holland's family was looked after.
"Together with Racing Victoria, the Jockey Assistance Program will be wrapping its arms around the riding group and will be working to support Lucy and the Holland family both now and importantly into the future," Mr Hyland said.
Anzac Day race meetings at Flemington in Melbourne and Moe in Victoria's Latrobe Valley won't go ahead out of respect for Holland.
The Australian Jockeys Association said it lost a cherished member of its ranks.
"Words can never describe the loss of a young person but to all family and friends we will send prayers and our deepest sympathies," the association said.
Melbourne Racing Club, which runs the Caulfield and Sandown tracks, said its thoughts were with Holland's family at an extremely difficult time.
The sentiments were echoed by the Victoria Racing Club and other racing bodies across the country.
Four-time Melbourne premiership-winning trainer Peter Moody, famous for preparing unbeaten sprinter Black Caviar, said Holland was gone way too soon.
Racing Victoria stewards have adjourned an inquiry into the incident to a date to be fixed.
WorkSafe is investigating the circumstances surrounding Holland's death.
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