Nick Rust will step down as chief executive of the British Horseracing Authority at the end of the year.
Rust has led the the BHA for five years but signalled his departure in a message to staff on Tuesday.
He said he had spent some time determining his future since the death of his wife Magarita in November 2018.
“I’ve spent much of the past year reflecting on my situation after my personal bereavement at the end of 2018,” Rust said.
“I wanted to let you and the BHA know my decision and plans well ahead of leaving to allow plenty of time for a successor to be identified and appointed.
“With the committed support of our new chair, Annamarie Phelps, the BHA has put itself, and helped put our sport, in a place where we can be optimistic about our future. The foundations for success are in place.”
The BHA confirmed it would begin the process of selecting a new chief executive in the next few weeks.
Rust, 52, succeeded Australian Paul Bittar at the head of the governing body in January 2015 following a near 30-year career in the betting industry at Ladbrokes, Coral and Sky Bet.
During his tenure, Rust was instrumental in racing’s successful bid to persuade the government to reform the levy system.