Studies indicate that mental health professionals stigmatise mental illness through the endorsement of negative stereotypes, emotions, and behaviours. While this is an important domain of research, existing literature on the stigmatisation of mental illness by mental health professionals and trainees is marked by many weaknesses. The objective of the current dissertation was to rectify several of these weaknesses with a program of research that involved three distinct studies. Study 1, a scoping review, aimed to describe the current state of research on the stigmatisation of mental illness by mental health professionals. Study 2 aimed to explore, through qualitative research, the mental disorders, stereotypes, emotions, and behaviours that are essential to the relative stigmatisation of mental illness by mental health professionals. Study 3 aimed to identify how key stereotypes and mental disorders relate to one another in a sample of trainee mental health professionals. [...]