While physical activity and exercise are well-established to be beneficial for physical health, the effects on mental health are also now becoming more apparent. Specifically, there is an increasingly large clinical and academic interest in how physical activity may be used to (i) reduce the risk of developing mental illness, and (ii) improve recovery and outcomes in those with diagnosed conditions. Within this, multiple national and international health bodies have begun to produce guidelines around the role of physical activity in the promotion of mental well-being. However, the overall evidence for if and how to use physical activity interventions in the prevention and treatment of various mental illnesses is unclear. Therefore, this presentation will aim to provide an update on the current state of the evidence on the benefits of physical activity across a broad spectrum of mental health conditions, such as depression, anxiety, bipolar and psychotic disorders, and ADHD. Within this, the published ‘top-tier evidence’ (including meta-analyses, randomized controlled trials, and Mendelian randomization studies) will be discussed, particularly with regards to determining the causal effects of physical activity on mental health/illness. Following this, an update of key recent international guidelines on the topic will be presented, along with an exploration of the emergent literature around how physical activity and exercise can be best implemented for improving outcomes in the context of mental healthcare.