It will be the most senior role at Guardian Labs following the departure of Anna Watkins, who had been managing director for almost three years.
Fox will be responsible for developing and leading the team producing content. She will report to Hamish Nicklin, chief revenue officer at GNM, and Caspar Llewellyn Smith, head of Guardian digital platforms.
Fox joined The Guardian’s fashion desk in 2004 and became head of fashion in 2013. During her time there, she helped launch its bi-annual supplement The Fashion.
Nicklin said: "I’m thrilled to have attracted a journalist of Imogen’s calibre into this exciting commercial role.
"In this newly-created position Imogen will use her deep understanding of The Guardian’s journalistic values to work directly with clients to deliver outstanding commercial results."