What are the biggest advertising agency holding companies?
The biggest advertising holding companies are Omnicom (which absorbed IPG in November 2025), WPP, Publicis Groupe, Dentsu and Havas. Each owns dozens of creative, media and data agencies. After the IPG deal, Omnicom reported pro forma revenue above $25 billion, placing it at the top by revenue, with Publicis and WPP close behind.
A holding company (holdco) owns agency networks rather than running a single agency. Their media arms buy huge volumes of advertising on behalf of clients, sometimes through their own trading desks or principal-based buying, which has raised questions about transparency and media rebates.
The landscape changed quickly in 2025: Omnicom bought IPG, WPP restructured its media arm as WPP Media, and Publicis continued buying data and commerce businesses. Revenue rankings shift with currency movements and reporting changes, so always check the latest annual reports.