Keller told PRWeek the search for her replacement would commence "soon".
Keller, who is an executive board member at the FT, made the announcement via LinkedIn, saying: "This has been a difficult decision because the FT is so much more than a job to me. It is a family and mission I am so proud to be part of."
She added: "Being on the front lines of its transformation over the past decade - alongside the supremely talented FT Board - has been my greatest honour and privilege."
The 2017 PRWeek Global Power Book inductee confirmed that she would remain in her post until spring 2018 to ensure the company could find "a strong successor".
Keller joined the FT in 2007 as head of communications in the Americas. In 2010 her role was expanded to include leading the global press office.
After being appointed global director of communications in 2013, Keller took on additional responsibilities in 2014 as senior vice president of corporate affairs for Pearson Professional, which was then the owner of the FT.
After 13 months, she moved to her current role with the FT, in which she splits her time between Austin, New York and London.