BACKGROUND:Comparative optimism, the belief that negative events are more likely to happen to others rather than to oneself, is well established in health risk research. It is unknown, however, whether comparative optimism also permeates people's health expectations and potentially behaviour during the COVID-19 pandemic. OBJECTIVES:Data were collected through an international survey (N = 6485) exploring people's thoughts and psychosocial behaviours relating to COVID-19. This paper reports UK data on comparative optimism. In particular, we examine the belief that negative events surrounding risk and recovery from COVID-19 are perceived as more likely to happen to others rather than to oneself. METHODS:Using online snowball sampling through social media, anonymous UK survey data were collected from N = 645 adults during weeks 5-8 of the UK COVID-19 lockdown. The sample was normally distributed in terms of age and reflected the UK ethnic and disability profile. FINDINGS:Respondents demonstrated comparative optimism where they believed that as compared to others of the same age and gender, they were unlikely to experience a range of controllable (eg accidentally infect/ be infected) and uncontrollable (eg need hospitalization/ intensive care treatment if infected) COVID-19-related risks in the short term (P < .001). They were comparatively pessimistic (ie thinking they were more at risk than others for developing COVID-19-related infection or symptoms) when thinking about the next year. DISCUSSION:This is one of the first ever studies to report compelling comparative biases in UK adults' thinking about COVID-19.