This entry reviews the concept of transformative learning. Transformative learning theory stresses a learning perspective for situations when actors in (self-)critical ways recognize and reassess basic assumptions and expectations that steer their thinking, feeling, and acting. The theory relies on the humanistic assumption that people have, via deliberative acts, inner capacities to change circumstances. Transformative learning is defined as the process through which actors transform problematic frames of reference. The concept has been applied broadly in sustainability studies, including environmental sociology. The entry discusses five such fields of research, with relevance for environmental sociology: (1) environmental and sustainability education research, (2) the role of emotions in relation to, for example, climate change, (3) research on environmental activism, (4) lifestyle change, and (5), on transformative learning on community/organizational levels.