Harri starts his new role in February. In November, Harri announced that he was to leave his position at The Sun and The Times publisher at the end of 2015 after three-and-a-half years, saying it was "job done".
In a statement issued this morning, Liberty Global said: "Based in London, Guto will lead external communications for Liberty Global and its senior executives and will report to Manuel Kohnstamm, Liberty Global’s SVP and chief corporate affairs officer."
Harri will be working with senior Liberty Global execs including president and CEO Mike Fries.
In his new role, Harri will again work in the same organisation as Tom Mockridge, former CEO of News UK’s predecessor News International and currently CEO of Virgin Media.
Harri, who left News UK on 18 December, previously worked as an aide to London Mayor Boris Johnson.
He began his career as a journalist at the BBC, covering the collapse of communism, the fall of the Berlin Wall and the first Gulf War. He rose to become the BBC’s chief political correspondent at Westminster and also had postings in Rome and New York.