Merseytravel chief executive Neil Scales is to step down after nearly 15 years with the organisation.
He is leaving Liverpool for Brisbane, Australia, where he will become the chief executive of the city's passenger transport executive TransLink.
Scales, who starts the job in March, said: "It was a hard decision to make and one I spent some considerable time agonising over but I have received an offer which was too difficult to refuse.
"For me this is a challenge to make a real difference on the other side of the world and an opportunity of a once-in-a lifetime experience 'down under'."
Merseytravel is owned by the authorities of Sefton, Wirral, Knowsley, St Helens and Liverpool and employs around 800 staff.
It is Merseyside's passenger transport executive and also owns and operates the Mersey Tunnels and Mersey Ferries.
Cllr Mark Dowd, chair of Merseytravel, said: "I have worked with Neil Scales for 15 years, and he has been a massive asset to Merseytravel and Merseyside.
"His expertise is not only known and appreciated here, but obviously overseas too, and this is a wonderful opportunity for him to further his career.
"He will be missed professionally, but it is also a great personal loss to me as both a friend and chairman, and to the organisation as a whole."
Scales, who has been chief executive since 1999, will leave in March. The search for a replacement will start soon.
In a message to Merseytravel staff he said: "I know I leave Merseytravel in good shape to face the future and I am proud of what we have achieved together.
"There is much I will miss, in particular the tremendous support I have received from you all during my time here. I truly thank you for your loyalty and hard work and wish you all every success in the future."