This article introduces the articles for the Ecopsychology special issue on ecotherapy. The articles are divided into two sections. The first part contains articles that apply ecotherapy to generalized mental health problems. The second part contains articles that use ecotherapy to address the psychological problems generated by climate change. Taken together both parts summarize a collaborative definition of ecotherapy. Ecotherapy is a psychotherapeutic technique where a clinician and a person seeking treatment make use of the relationship with their ecosystem and its history to internalize new, positive, and enduring psychological constructs.