John Feehan has stepped down as chief executive of the Six Nations and British & Irish Lions with immediate effect.
Feehan has held the post for the past 16 years, overseeing growth in the most popular annual international competition and a total of four Lions tours.
The process of appointing his successor is to begin shortly with Ian Ritchie and Sir Clive Woodward possible candidates.
"I feel it is time for a change. I have thoroughly enjoyed every minute working in both roles, but the timing is right for me and I'm ready to pursue other interests," Feehan said.
"I depart safe in the knowledge that both organisations are in a significantly better place than when I started and both have a very bright future ahead.
"I would like to acknowledge the fantastic people I have worked with over the years and look forward to watching rugby as a passionate supporter for many years to come."