Denney will report to the executive creative director, Steven Bennett-Day, who joined Havas EHS from FCB Inferno in January, and will work on Unilever accounts including Simple, Cornetto and Dove.
Havas EHS was named the global digital agency for Dove and another Unilever brand, Surf, in 2013. It picked up the Dove Men+Care business earlier this year.
At Havas Worldwide London, Denney was the digital creative director for brands such as Veet and Credit Suisse.
Earlier this year, Havas EHS hired Richard Clarke as a creative technologist and promoted the associate creative director Aaron Howard to creative director. Sarah Wood was promoted to replace Howard.
Bennett-Day said: "This really puts creativity at the heart of our business. All the insight we gain from our data expertise now has a brilliant team of people to bring it to life."