We evaluated the association between individual-level socioeconomic status (SES), life expectancy, and mortality, in adult men and women from the general population living in Catalonia, a universal healthcare coverage setting. We used the Catalan Health Surveillance System database, which includes individual-level information on sociodemographic characteristics and mortality for all residents of Catalonia (Spain). We categorized individuals as high, medium, low or very low SES based on annual personal income and welfare receipt. We used 2016 mortality data to estimate life expectancy at age 18, and the probability of death by age, sex and SES categories. We followed a total of 6,027,424 Catalan residents in 2016. Men and women of very low SES had 12.0 and 9.4 years lower life expectancy compared to men and women of high SES, respectively. Low SES was also strongly associated with mortality in both men and women of any age. In the entire adult population of Catalonia, despite the availability of universal, high quality healthcare coverage, low SES is associated with lower life expectancy and higher mortality. Solutions to these large inequalities may combine tailored health promotion and management interventions, with solutions coming from outside of the health sector.