Affective computing has been an active area of research for the past two decades. One of the major component of affective computing is automatic emotion recognition. This chapter gives a detailed overview of different emotion recognition techniques and the predominantly used signal modalities. The discussion starts with the different emotion representations and their limitations. Given that affective computing is a data-driven research area, a thorough comparison of standard emotion labelled databases is presented. Based on the source of the data, feature extraction and analysis techniques are presented for emotion recognition. Further, applications of automatic emotion recognition are discussed along with current and important issues such as privacy and fairness.