Left-wing approaches to the environment, ecological questions and green issues are as complex as ‘left-wing’ thought itself. While there are a wide variety of schools of thought which one can label as ‘left-wing’, ranging from revolutionary Marxism-Leninism, Maoism, Trotskyism, communism, to trades union activism to reformist social democracy, to anarcho-syndicalism, anarchism and much more, this chapter will confine itself to two main historical trends in left-wing social theory and action, namely Marxism and anarchism.