During the 2020 COVID-19 pandemic, one of the key components of many countries' strategies to reduce the spread of the virus is contact tracing. To explore public attitudes to a COVID-19 contact tracing app in the United Kingdom. Online video-conferencing. 27 participants, UK residents aged 18 years and older. Qualitative study consisting of six focus groups carried out between 1st-12th May, 2020 (39-50 days into the UK 'lockdown'). Participants were divided as to whether or not they felt they would use the app. Analysis revealed five themes: (1) lack of information and misconceptions surrounding COVID-19 contact tracing apps; (2) concerns over privacy; (3) concerns over stigma; (4)concerns over uptake; and (5) contact tracing as the 'greater good'. Concerns over privacy, uptake and stigma were particularly significant amongst those stated they will not be using the app, and the view that the app is for the 'greater good' was particularly significant amongst those who stated they will be using the app. One of the most common misconceptions about the app was that it could allow users to specifically identify and map COVID-19 cases amongst their contacts and in their vicinity. Our participants were torn over whether digital contact tracing is a good idea or not, and views were heavily influenced by moral reasoning. No patients were involved in this study. The public were not involved in the development of the research questions, research design or outcome measures. A pilot focus group with participants not included in the present paper was used to help test and refine the focus group questions. Summary results were disseminated via email to participants prior to publication for feedback and comment.