Optus chief executive Chris Anderson is planning to vacate his position in August.
Optus' parent company Singapore Telecommunications said Anderson will step down and make way for Optus COO Paul O'Sullivan.
Anderson has held the chief executive post at Optus for seven years, a period which included the company's acquisition by SingTel.
SingTel president and chief executive officer Lee Hsien Yang said Anderson has done a remarkable job turning the telco into a major force for competition and regulatory reform in Australia's telecommunications sector.
Anderson said he will be leaving at a time when Optus is trading strongly and growing at three times the industry average.