His impending departure from the SPL follows his resignation from the Scottish FA board in the spring.
In a statement released by the Premier League, Topping said: “I have enjoyed my time chairing Scotland’s premier sporting competition.
“Unfortunately, with the ongoing international expansion of William Hill, involving regular and substantial long-haul travel, I will be unable to devote sufficient time to the SPL over the next few years to do the role justice.
“It is therefore with regret, and to be fair to the clubs, that I feel I must step down from the SPL to focus 100% on William Hill.”
SPL chief executive Neil Doncaster added: “Since his appointment in October 2009, Ralph has been a powerful and influential advocate of Scottish football and has steered the league through a very challenging period.
“On behalf of the entire SPL board, member clubs and staff of the league, I would like to extend our sincere gratitude to Ralph for his hugely significant contribution and wish him the very best of luck for the future.”
According to the statement, ‘the process for appointing a new independent non-executive chairman of the Scottish Premier League will begin immediately’.
Back in July this year, Scotzine contributor John Stone questioned Ralph Topping’s position as SPL chairman, given the conflict of interest there was given his position with William Hill.