Betting firm Ladbrokes have signed a three-year deal with Arena Leisure, the management company of Doncaster racecourse to sponsor the St Leger. This year's race will have a prize fund of �450,000, making the world's oldest Classic one of Britain's richest races.
This year's race - the 229th running - will be on 10 September.
Chris Bell of Ladbrokes also announced that any colt able to win this year's 2000 Guineas, the Derby and the St Leger would land a �1m bonus.
Ian Penrose, chief executive of Arena Leisure, said: "Being the oldest Classic in the world, the St Leger is steeped in turf history.
"We are determined to build on this and to ensure that, through our partnership with Ladbrokes, this great race is restored to its former glory.
"In recent years, all of us who value the St Leger will have been encouraged by the upsurge in the racecourse attendance.
"The 2004 running attracted in excess of 26,000 race-goers compared with a crowd of just over 18,000 in 1995."