Background/Purpose: Mental illness is highly stigmatized and viewed negatively by the public. Stigma is associated with several poor health outcomes for persons living with mental illness, which can be mitigated through social support. Media exposure shapes the public’s knowledge, attitudes, and beliefs. Therefore, people may develop stigmatizing attitudes through media exposure. Studies of mental illness stigma have historically focused on traditional media, such as print news, which often perpetuate stigma. The purpose of this dissertation is to provide novel methods through which to examine mental illness stigma and social support by exploring these topics across multiple social media platforms. Methodology: This dissertation employed Twitter, Instagram, and qualitative interview data to explore mental illness stigma and social support through current events, geographic location, and responses to the culture of social media. This mixed-methods approach used content analysis of social media and qualitative interview data, as well as machine learning techniques, to describe the ways in which stigma and social support manifest on these platforms. Results: We found that social media content contained both overt and covert mental illness stigma and that some of this stigma was counteracted by displays of social support, which were prominent during high volume communication periods on social media. However, stigma on social media demonstrated a potential to be internalized as self-stigma, which was shown to be discouraging to support-seeking on these platforms. Conclusions: This research demonstrates the need for mental health advocacy on social media at both the individual and organizational levels. Considering these findings, advocates should mobilize on social media during current events related to mental health. Advocacy should be defined by stigma reduction, displays of social support, and encouragement of support seeking on these platforms.Dr.P.H., Community Health and Prevention -- Drexel University, 201