The largest continent is Eurasia (Europe and Asia combined) at 21,100,000 square miles (54,649,000 square kilometers). But even if you consider Europe and Asia to be two separate continents, Asia is still the largest, at 17,300,000 square miles (44,807,000 square kilometers).
A satellite image showing the continents of North (1) and South America (2), Europe (3), Asia (4), Africa (5), Australia (6), and Antarctica (7). (Image courtesy MODIS Land Group/Vegetation Indices, Alfredo Huete, Principal Investigator, and Kamel Didan, University of Arizona).