Barber has been editor since 2005, leading the newspaper to become the pre-eminent business broadsheet in the world.
As FT editor, he has interviewed many world leaders including President Barack Obama, Chancellor Angela Merkel, President Hassan Rouhani, President Donald Trump, President Vladimir Putin, Premier Li Keqiang and President Cyril Ramaphosa, as well as the most influential people in world business.
The newspaper has won prestigious awards for its journalism, including from the British Journalism Awards, Gerald Loeb, Overseas Press Club, Society of American Business Editors and Writers and Society of Publishers in Asia.
"After 14 years, I am stepping down as editor, effective January 2020. It’s been a rare privilege and pleasure to hold the best job in journalism," Barber said.
"When I took over as editor, I pledged to restore the gold standard in the FT’s reporting and commentary, and to help the board to build a sustainably profitable business based on digital transformation.
"Since Nikkei purchased the FT in 2015, I have also worked hard to cement our global media alliance. Together we have achieved these goals, passing the milestone of one million paying FT readers (75 per cent of readership) this year."
Tsuneo Kita, chairman of the FT’s proprietor, Nikkei, commented: "It’s been our utmost privilege to have worked with Lionel. He has transformed the FT newsroom into a world class digital-first operation, producing a unique combination of deep, original reporting and powerful commentary. FT journalism has never been stronger.
"We also thank him for his commitment to the successful partnership between the FT and Nikkei, navigating an unprecedented collaboration between the two newsrooms. He is a strategic thinker, true internationalist and great friend of Nikkei."
Barber began his career in journalism in 1978 as a reporter for The Scotsman, before moving to The Sunday Times three years later.
He joined the FT in 1985 as a business reporter and a year later became Washington correspondent before being appointed Brussels bureau chief in 1992.
He served as the news editor from 1998 before leading the continental European edition between 2000 and 2002. He was then appointed US managing editor, before moving back to London as editor.
Barber has co-written several books and lectured widely on foreign policy, transatlantic relations and Europe.
Khalaf, who has been at the FT for 24 years and served as deputy editor, associate editor and Middle East editor, confirmed on Twitter that she would take the reins of the FT newsroom.