When Collins joins the agency in the summer he will form a new management team at Fallon alongside Nick Bell, the executive creative director, and David Hackworthy, the chief strategy officer.
Collins returned to the UK a year ago after five years in a managing partner role at Clemenger BBDO in Sydney. He had previously worked at AMV and came back to run its Sainsbury’s account, overseeing the award-winning Christmas campaign set on a First World War battlefield.
Magnus Djaba, the chief executive of Saatchi & Saatchi Fallon UK Group, said: "When Pat Fallon picked a management team to start Fallon London, he chose people who didn’t know the rules but just wanted to create new ones. Gareth has that same spirit and attitude."
Collins said his aim is to "get Fallon back on its pedestal".
He added: "It has a history and culture of brilliant work, great people and fantastic clients, and the market is crying out for an agile agency that can challenge the big guys."
Fallon was considered one of the most successful creative agencies of the noughties but has stuttered since its founders moved on. Gail Gallie, who had been chief executive since 2010, then left the agency in April last year.
Collins’ arrival coincides with the departure of Fallon’s managing director, James Townsend, who is joining the digital agency 360i as its chief executive.