Jamie Stier is to leave his position as chief regulatory officer at the British Horseracing Authority to take up a role in his native Australia.
The BHA said a departure date has not yet been finalised, but that Stier will leave during the first half of 2018.
BHA chief executive Nick Rust, said: "Jamie has made a significant contribution as chief regulatory officer, and in his previous roles at the BHA since he joined in 2010. I would like to thank him for his work, and wish him well for the future."
He added: "Our system of regulation has been improving and becoming much more transparent and progressive over the last few years.
"I shall be looking for a successor for Jamie to take forward a number of key projects he has been involved in, bringing them to fruition by collaborating with all in our sport so that we can achieve our vision of a brighter future for British racing."
Stier said: "I have greatly enjoyed the privilege of working in British racing, and more particularly the BHA, during the last eight years.
"I have been fortunate to have worked with many fantastic people during my time here and the current team guiding the BHA, under Nick's leadership, is no exception. I would like to thank those who have offered me support during my time here.
"I will leave comfortable in the knowledge that the BHA is committed to consistently looking at ways in which the sport can be most effectively regulated to safeguard the reputation of racing and all those involved in it, including the real stars of the show, the horses."
Select any odd to add a bet