What is the largest ad agency in the US?
By revenue, the largest US-based advertising agencies in 2026 belong to the four major holding companies — WPP, Omnicom, Publicis, and Interpublic. Individual agency ranking shifts year-to-year, but Ogilvy, BBDO, McCann, Publicis Worldwide, and DDB consistently sit in the top 10 by US billings. Independent agencies rarely crack the top 20 by revenue but often lead in creative recognition.
Why this matters
This question shows up regularly in Google's People Also Ask for the "marketing agency" query, which is a signal that buyers in this space are asking it constantly during their research phase. The answer above is written from The Wall's editorial position — we index 2,286 verified US growth-services vendors across 10 pillars and see how these questions map to actual buying decisions.
If you're evaluating vendors in this category, the Marketing pillar page has the full US firm list with rates, team sizes, and headquarters filters.