["The Journal of Industrial Economics, Volume 74, Issue 1, Page 60-101, March 2026. ", "\nABSTRACT\nIn this paper, we empirically study how flagship entry in an online marketplace affects consumers, the platform, and various sellers on the platform. We find flagship entry may benefit consumers by expanding the choice set, by intensifying price competition within the entry brand, and by improving consumer perception for parts of the platform. In the meantime, flagship entry cannibalizes the sales of same‐brand sellers, while other brands may gain as the buyer base expands on the platform. Counterfactual simulation suggests that flagship entry improves the gross merchandise value (GMV) of the platform and overall consumer welfare in most cases.\n"]