Ryan joins the agency today (14 January) and will work across all Cheil clients, including Samsung, Coca-Cola and Crocs.
She replaces Logan Wilmont, who left in April 2015, and will report to Paul Hammersley, Cheil’s group chief executive.
Ryan was the group executive creative director at Karmarama between 2013 and 2015. She left the agency shortly after the arrival in May last year of Nik Studzinski, the chief creative officer, from Droga5 London.
Hammersley said: "Caitlin understands how modern brands connect with consumers. She will be a powerful force in helping to drive the next phase of our growth."
Ryan previously spent 14 years at Proximity and rose to executive creative director. She was behind "mission control" for Procter & Gamble, which won three golds at the 2012 DMA Awards.
She said: "Cheil champions diversity, invention and entrepreneurialism, which makes it the perfect home for me. The network’s media-agnostic approach is conducive to the best creative ideas, inspired and informed by consumers’ lives."