This historical study identifies catalysts for transformative learning in the lives of three scientist-environmentalists important to the 20th-century environmental movement: Aldo Leopold, Rachel Carson, and David Suzuki. Following a brief review of theoretical perspectives on transformative learning, the article argues that transformative learning for these scientists was catalyzed by certain "disorienting dilemmas" and was both rational and emotional. Moreover, the personal transformative learning of each scientist helped provoke a process of transformative learning in society at large: Leopold's contribution to the founding of the disciplines of wildlife conservation and restoration ecology, and his "land ethic" fostered the development an ecological consciousness in the 1940s; Carson's "Silent Spring" helped provoke the environmental consciousness of the 1960s; and Suzuki's public environmental education and activism from the 1970s to the present-day played an influential role in North American environmental movement.