Telstra chief executive Sol Trujillo is leaving the company and returning to the United States.
Mr Trujillo, who took up his role in Australia in July 2005, will leave the company on 30 June, Telstra said on Thursday as it reported a 1% dip in first half profit.
Chairman Donald McGauchie said Mr Trujillo and the Telstra board had agreed that now was a suitable time for a transition to a new chief executive.
The board "is well prepared with succession planning and will now formally commence a wide-ranging search for a suitable successor", Telstra said.
A new appointment is expected by the end of June.
"On behalf of the Telstra board I would like to congratulate Sol on his outstanding leadership and extraordinary achievements," Mr McGauchie said.
"His vision, strategic direction and commitment to execution have positioned Telstra as a media communications company with a wide range of options for ongoing growth."
Telstra said Mr Trujillo had discussed his intentions to leave the company with the board on Wednesday.
He said he would continue to drive the business until his departure at the end of June.
"The results we have achieved together over the past four years make me incredibly proud. I have every confidence that Telstra will continue to deliver world-leading results for shareholders."
Telstra announced on Thursday that its net profit for the six months to December was $A1.916 billion, down 1% on $A1.926 billion in the previous corresponding period.
Revenue for the first half was $A12.71 billion, up 3% on $A12.372 billion in the previous corresponding period.