Williams, one of the most high-profile strategists in the industry, leaves Mother after nine years. His start date at Publicis has not been set.
In his new role, he will be charged with developing the network’s global strategy and innovation.
He will be based in Publicis UK’s London office and report directly to Arthur Sadoun, the chief executive of Publicis Worldwide.
Williams joined Mother in 2005 as its first head of strategy. He previously worked at Bartle Bogle Hegarty, latterly as a board account planner.
Williams is known for his involvement in entrepreneurial business and technology, and leads Mother’s participation in Tech City, London’s start-up hub. He sits on the Government’s Tech City advisory board and founded Mother’s start-up incubator, Mother at The Trampery.
Sadoun, who was promoted to chief executive of the network in July last year from the role of managing director, said hiring Williams was the second step in his plan to boost the UK operation after buying the digital agency Poke from Mother in September 2013.
In the UK, Publicis Worldwide includes Publicis London, Publicis Chemistry, Publicis Blueprint and Poke.
Sadoun said: "Dylan is fulfilling two of my top priorities. The first is to make Publicis Worldwide recognised as the most strategic creative network.
"The second is to put London at the centre of our map. We are strong in France and Germany, but we want to be even stronger in the UK."
He added: "Dylan is an inspiring leader and has knowledge of technology through everything he does outside of pure advertising, which is the route we want to follow."