Which South American country has the most Spanish speakers?

Colombia has the most Spanish speakers of any country in South America.

Spanish is Colombia’s official and overwhelmingly dominant language, spoken by more than 99% of the population. With a population exceeding 50 million, that gives Colombia the continent’s largest Spanish-speaking population, ahead of Argentina, Peru and Venezuela.

Colombian Spanish is not a single uniform accent. Coastal varieties show Caribbean influence, while highland speech—especially the variety associated with Bogotá—is often noted for its conservative pronunciation and high social prestige. Colombia also recognizes and protects many Indigenous languages and two important Creole languages, so Spanish dominance does not mean the country is linguistically uniform.

The question is limited to South America. Worldwide, Mexico has more Spanish speakers than Colombia, and the United States also has a very large Spanish-speaking population. Another mix-up is confusing the largest Spanish-speaking population with the largest Spanish-speaking country by area; Argentina is geographically larger, but Colombia has more speakers.