Acclaimed journalist Sarah Ferguson will replace Kerry O'Brien as the new presenter of the ABC's flagship investigative program, Four Corners.

O'Brien signed off from Four Corners last night after five years in the presenter's chair, and more than 40 years with the national broadcaster.

"There is no place I would rather be," Ferguson said.

"Four Corners has the past nailed and a future full of promise and excitement. A big thank you and farewell to Kerry O'Brien."

ABC Current Affairs head Bruce Belsham said the role was a perfect fit for Ferguson.

"It's fantastic that Sarah has agreed to succeed Kerry O'Brien as host of Four Corners," he said.

"It's a great fit given Sarah's history with the program and her stature in Australian journalism. It also allows her to combine presenting with her brilliant reporting from the field."

Ferguson previously worked on Four Corners from 2008 until the end of 2013, winning a number of awards during her time there, including the Gold Walkley.