Today’s university students are tomorrow’s leaders, decision makers, workers and parents, and will shape the economy and society (Dietz et al. 2020). A sense of crisis has developed around the mental health (MH) of these students (Higher Education Policy Institute 2016; Institute for Public Policy Research 2017). Demand for already-overstretched support services is rising (Institute for Public Policy Research 2017). The burden on these reactive, individual services may be alleviated by shifting focus from individuals to institutions, and embedding prevention-based initiatives into the education system (PHE 2015). The benefits of regular physical activity (PA) for MH and wellbeing are well known (Dietz et al. 2020). Recent reviews demonstrate that PA interventions improve wellbeing and quality of life in adolescence (Hale et al. 2021; Piñeiro-Cossio et al. 2021), and reduce feelings of distress and depression (Heinze et al. 2021) in students (Gondoh et al. 2009; Nabkasorn et al. 2005). Crucially, PA not only benefits those who are struggling but can also prevent mental ill-health (Pascoe and Parker 2019; Heinze et al. 2021) and the benefits of PA are felt even when conducted at low or mild intensity (Smith, Ekelund, and Hamer 2015). Despite the benefits of PA, rates of this activity decline throughout adolescence (Hale et al. 2021); 80% of adolescents globally fail to meet guideline recommendations of 150mins of PA per week (van Sluijs et al. 2021). The decline may arise partly because adolescents are no longer exposed to comprehensive, school-based PA programmes, as the focus shifts to GCSEs and A-levels, or equivalent (van Sluijs et al. 2021). School-based programmes support PA not only via PE lessons and sports, but also through three forms of classroom-based PA: physically active learning, curriculum-based activity breaks, and non-curriculum breaks (Watson et al. 2017). Despite calls to integrate PA into the curriculum (Kupchella 2009; Levitsky et al. 2006), there is little evidence of any systemic approach to PA promotion in UK universities. The need to embed PA into the university education experience has grown more acute since the COVID-19 pandemic, as universities have embraced blended delivery (i.e. part online, part in-person), which likely incurs even lower levels of instrumental PA (Maguire, Dale, and Pauli 2020). An effective, embedded PA programme must consider the demands and practices of the post-pandemic university and be co-designed with stakeholders. This project will develop an approach to embed PA in the university educational experience to increase PA and enhance mental health. We will specifically focus on embedding PA into the educational component of the university experience, because this is common to all institutions, – yet often is neglected when considering MH and wellbeing interventions. We will follow a systematic intervention development approach (the ‘Behaviour Change Wheel’, Michie, Atkins, and West 2014). First, through qualitative interviews with stakeholders, we will seek to develop a systems map to identify how student PA is facilitated or hindered within the university education system. Secondly, we will run stakeholder workshops to identify key sites within the system at which PA might be embedded, and co-design intervention strategies. Finally, we will assess the feasibility and acceptability of an intervention embedding PA into this system.