How research is assessed affects what types of knowledge are valued, incentivized, and rewarded. An increasingly important element of contemporary research evaluation is the measurement of the wider impact of research (e.g. benefit to society, culture or economy). Although the measurement of impact has been highly contested, the area is under-theorized and dominated by pragmatic research policy imperatives. Informed by a sociological perspective, this article intervenes in this context by reframing research impact as the attainment and maintenance of capital (i.e. symbolic power or status) in various fields beyond academia. It argues that research impact occurs at the intersection of these fields of power. The article shows that impact involves various combinations of capital from the scholarly field, the field of politics, the field of application, the media field, and the economic field, which provide credibility, authority, utility, visibility, and weight, respectively. In exploring the forms of worth and value that underpin the pursuit of legitimacy in these fields, the article provides a new theoretical framework for understanding research impact and its assessment.