What are the origins of the Israeli–Palestinian conflict? In this article, I shed new light on the beginnings of Zionist colonization and the Israeli–Palestinian conflict by focusing on the effect of malaria on labor competition in late-Ottoman Palestine. In doing so, I develop a bioterritorial theory of colonization; I propose that disease can profoundly shape territorialization, labor regimes, political-economic development, and intergroup conflict over labor and land. In dialogue with Du Bois’s work on collectivist colonization in closed labor markets, I use this bioterritorial theory to understand early economic competition between Jews and Arabs. I show how disease shaped this competition by undermining malaria-naïve Jewish workers, who consequently struggled to survive in the country. I propose that malaria was a highly important factor driving the Jewish workers to ally with the World Zionist Organization in pursuit of exclusivist collective settlements, thereby shifting their focus from labor to land. To develop this argument, I draw from historical data, including memoirs, newspaper articles, reports, letters, and scientific publications. The bioterritorial theory contributes to scholarship on settler colonialism, theories of disease and colonization, and explanations of colonization and conflict that focus on ideology and ethnonationalism.