Title: Meaningful for whom? Exploring ‘meaningful involvement’ in co-design for people who live in aged care. Background ‘Meaningful involvement’ is a term regularly used to describe participation in co-design, however, the perspective from which ‘meaning’ is defined is rarely made explicit. We aimed to foreground the perspectives of people living in residential aged care, to identify the key components of what ‘meaningful’ involvement means for this group. Methods Semi-structured interviews with participants from three aged care organisations, across three Australian states. Participants were staff or self-nominated. Interview questions explored what meaningful involvement looks like from resident perspectives, and interviewees identified a preferred level of participation in a hypothetical co-design research or continuous improvement project, guided by the IAP2 Spectrum of Public Participation (inform, consult, involve, collaborate, empower). Analyses included deductive and inductive approaches. Results Twenty interviews were conducted (NT [N=6], QLD [N=7], VIC [N=7]). Participants identified varying levels of participation preference, ‘involve’(55%), ‘collaborate (20%), ‘consult’(15%), ‘inform’(5%), ‘empower’(5%). In general, regardless of preferred participation mode, ‘meaningful’ participation appeared to depend on observation of evidence that i) an individual’s perspective informed the resulting research project and/or ii) participation led to change. Emerging themes suggested meaningful involvement in co-design includes ‘feeling listened to’, ‘feeling respected’ and ‘seeing change happen’. Conclusions This is the first study to directly interrogate the notion of ‘meaningful’ involvement in co-design from the perspectives of people living in residential aged care. Without clarifying residents’ expectations and understandings, co-design in this setting risks being superficial, wasting resources and potentially causing harm to residents.