This book introduces readers to the principles of a fairlynew branch of psychology – positive psychology – and demonstrates how they canbe applied in the context of second language acquisition in a naturalenvironment and in instructed foreign language (FL) learning. It focuses bothon the well-being and success of the learner and the professional and personalwell-being of the teacher. Further, the book stresses the importance of thepositive emotions and character strengths of those involved in the process oflanguage learning and teaching, as well as the significant role played byenabling institutions such as school and, at the micro-level, individual FLclasses.