Optus chief Kevin Russell will step down at the end of March, just over two years after taking the post.
Paul O'Sullivan,currently group consumer chief executive at Optus' parent company Singapore Telecommunications, and a former CEO of Optus, will act as an interim boss while the company seeks a long term replacement.
The recruitment process is already under way, Optus said.
Mr O'Sullivan said Mr Russell had flagged his intention to leave several months ago, while he was helping reposition the company.
"Several months ago Kevin told me that he wished to move on to other challenges on completion of this phase, after ensuring an orderly transition that embeds the strategic transformation he has led," Mr O'Sullivan said.
Mr Russell joined Optus as chief operating officer early in 2012, before shifting to his current role in March of that year.
