"After more than 40 years of reading other people's press releases, it's a very strange feeling having to write one about myself," he said in a press release from the ABC.
However, this is not a complete retirement for O'Brien, who intends to take a year off to assess his options before deciding which direction to continue his career.
"Quite simply it's time for a new chapter."
"I've been in the pressure cooker of daily current affairs hosting and interviewing for 21 years including six years at Lateline and it's been something of a marathon."
"This has been a great year for the program, and it's good to leave on a high note."
O'Brien has generally remained popular with the audience, and for this he was grateful. "I would also like to thank an extremely generous audience, including those who may have occasionally thrown a shoe at the screen," he said.
But how easy will it be to replace such an iconic newscaster remains to be seen -- the ABC has quite a challenge on its hands.
Will you miss your nightly dose of Australia's favourite "ranga"? Who do you think should replace him?