The outspoken marketer, who joined William Hill in 2010 from Yahoo, was a member of William Hill’s senior executive team and was instrumental in doubling the market capitalisation of the business and in its re-entry into the FTSE 100 for the first time in seven years.
Fahy joins Telegraph Media in April as chief marketing officer, when he will become a member of the publisher's senior executive team and will report to chief executive Murdoch MacLennan.
Before joining William Hill, Fahy was Yahoo’s vice-president of international marketing until his departure in 2009.
He has also held roles including brand marketing director for Blackberry and has a number of marketing posts at Orange.
MacLennan said: "Kristof has a proven track record of digital marketing across a range of industries. He will be a great asset to the fantastic team here at the Telegraph."
Fahy is a well known figure on the conference circuit, with a reputation for making blunt and often contentious comments.
At BrandMAX in December, he told brands not to over-complicate content and measurement by "disappearing up their own arse"; while he told an audience at Marketing’s Mobile 2014 conference to stop obsessing with ROI and "just get on with it".
He was one of the marketers to feature in Marketing’s Power 100 at the end of last year.