This article aims to explore the definitions and approaches of sustainable development (SD) in UK higher education institutions (UKHEI). Specifically, the article investigates how SD and education for sustainable development (ESD) are defined and enacted from the official websites of the 24 Russell Group Universities. The findings reveal that some of these universities disclosed their institutionalised sustainability conceptualisation with specific targets; more than half of these universities did not disclose their institutional definitions. Despite this inconsistency, all of the universities have recognised the importance of sustainability and SDGs and prioritised one or multiple dimensions of sustainability. Sustainability is implemented in UKHEIs mainly through four categories of activity: the learning environment, Research SDGs, external collaboration, and curriculum integration. This article found that sustainability has been routinised and systematically integrated by these universities regardless of their institutionalised sustainability conceptualisation. A more innovative path, however, is needed to ensure that sustainability transitions from being merely a strategic priority to an institutional ethos that drives all actions and decisions in these universities.