Sedentary behaviour (sitting time) holds public health significance as it is associated with detrimental effects on morbidity and mortality. The objective of this thesis was to examine the prevalence and socio-ecological correlates of sedentary behaviour amongst university students, with an emphasis on ethnic minority university students. The socio-ecological model of sedentary behaviour was employed as a theoretical framework to inform a series of regression models that identified the intrapersonal, interpersonal, perceived environmental, behaviour setting and policy-related correlates of sedentary behaviour. These models were estimated using secondary data from the Health Survey of England (HSE) and primary data collected at a London university. In Study 1 there was a focus on measuring the prevalence and intrapersonal correlates of sedentary behaviour in sub-samples of university students drawn from two waves of the HSE (2008 and 2012). Study 1 measured sedentary behaviour with two questions about time spent sitting watching television or for any other activity both on weekdays and weekends. In Study 2, primary data from a sample of 340 students was analysed and there was focus on socio-ecological correlates of sedentary behaviour at a university with a large ethnically diverse student population. Study 2 utilized the Marshall sitting questionnaire that collects data about domain-specific sedentary behaviour that includes: sitting at work, during travel, sitting at university, sitting for leisure time without watching television, sitting at home using computer and watching television both on the weekdays and weekends. Study 1 revealed that students in England spent around six (± 1.4) hours/day sitting, comparable with the general population. The intrapersonal and some interpersonal factors, such as age, ethnicity, physical activity, mental wellbeing and health-related quality of life, were statistically significantly associated with sedentary behaviour. Study 2 found that students at the London university spent on average 11.7 ± 3.3 hours/day sitting (mainly sitting at university or using a computer), nearly twice that of the general population in England. In Study 2, gender, employment status, income, social status and place of residence were statistically significantly associated with sedentary behaviour. In a subgroup analysis of ethnic minority students versus White students, gender, income, and employment status were significantly associated with sedentary time among ethnic minority students, whereas among White students only social class was significantly associated with sedentary time. Overall, the socio-ecological correlates found to be more strongly associated with sedentary behaviour in White and ethnic minority students were intrapersonal and interpersonal factors rather than environmental factors. Interventions and university policies targeting the intrapersonal and interpersonal correlates of sedentary behaviour may prove successful in reducing sedentary time amongst university students.