Paul Bittar is to leave his role as chief executive of the British Horseracing Authority when his three-year term ends next year.
Bittar was appointed in September 2011, having previously worked for Racing Victoria in Australia and for New Zealand Thoroughbred Racing.
The Australian will be involved in the appointment of his successor and that process has already begun, with an announcement due in the autumn.
Bittar said: "I am proud of what BHA has achieved in the past few years and it will be with some sadness that I will leave early next year.
"Despite its obvious challenges and complexity of structures, British racing is a world-class sport to be involved in and it has been a privilege to have held the post of chief executive of BHA, as well as lead such a committed team.
"I love the quality and diversity of the racing staged in this country, I'll never tire of it, and nowhere else can rival it in that regard."
Bittar's tenure has seen the BHA's financial position take on a much firmer footing, highlighted by the five-year £40million funding deal with Betfair and the four-year levy agreement with the big four retail boookmakers.
He has, however, needed a thick skin at times following the introduction of controversial new whip rules, significant changes to the Grand National course and, of course, the Mahmood Al Zarooni drugs scandal.
Bittar said: "There are many areas in which we have made significant progress.
"The opening weeks brought the challenge of resolving the dispute over the whip rules, followed by a difficult Grand National.
"It is encouraging and satisfying that the collaborative approach adopted by BHA with the relevant parts of the industry, and the subsequent steps taken, mean that neither topic has since generated the levels of negative coverage that can impact on the sport's well-earned and good reputation.
"We've consciously sought, and have seen, a fundamental change for the better with regard to our relationship with the betting industry, while our strategy of engagement with Government over the funding of British racing has also started to pay dividends.
"Our primary role is the regulation of the sport, so arguably the greatest challenge the sport faced during this period followed the positive tests for anabolic steroids in horses trained by Mahmood Al Zarooni.
"The gravity of the case warranted swift and decisive action, and in years to come it may well be seen as the catalyst which led to a material change in how racing around the world deals with the threat posed by the use of anabolic steroids.
"On this matter BHA has adopted, and I am sure it will maintain, a key leadership role in raising standards and seeking robust and rigorous international minimum standards.
"The outlook for British racing is significantly more positive now than it was at the close of 2011 and I firmly believe that the reputation of BHA has also improved. We have created a platform from which the sport can really grow and thrive.
"I'm focused on supporting Steve (Harman, chairman) and the board in ensuring that we achieve a lot before I finish.
"The back half of 2014 sees finalising of the 2015 fixture list, Government consultations on the offshore levy and levy reform, finalising of more formal and collaborative structures with our shareholders, and the next stages of the industry's growth strategy to name a few.
"I look forward to continuing to work effectively with the executive, board and shareholders on these subjects over my final six months."
Harman said: "On my arrival in summer 2013, I was delighted that Paul agreed to stay on until early 2015, and by having planned this timing we are in a good position with simultaneous developments with the BHA Board, shareholders, executive team and the implementation of the industry's growth strategy.
"The search for a new CEO has started and Paul's successor will be announced in the autumn.
"Paul is reviewing a number of options which he is considering for his next role, and I know he will make a big impact in whichever of the positions he chooses."
Bookmakers Paddy Power opened betting on the identity of Bittar's replacement and quote Winfried Engelbrecht-Bresges, the chairman of the Hong Kong Jockey Club, as 10/1 favourite, ahead of Rachel Hood, Charles Barnett, Edward Gillespie and Alan Byrne at 14/1.