Research capacity building (RCB) is an umbrella term that refers to the development in Low and Middle income countries (LMICs) of capacities for undertaking research (broadly construed). It is generally used very loosely to define a variety of activities whose ultimate aim is to empower individuals, organisations and systems to produce and use knowledge to achieve desirable social outcomes (better health, education, etc.). Within this broad remit, the focus of this paper is on RCB activities mediated via Official Development Assistance (ODA) and related kinds of donor-funded projects, programs and partnerships involving collaboration between LMICs and High-Income countries (HICs). Whilst much has been written recently on the need for these collaborations to strive to be as equitable as possible, less has been said about how their capacity building activities contribute (or not) to reduce inequalities, both within the partnership and in LMIC societies through their development impact. The paper critically examines current understandings and approaches to RCB through a social justice lens, flagging up inadequacies and offering an equity framework based on three broad principles of inclusivity, accessibility and sustainability as a starting point to bring different voices and perceptions of value into the design and evaluation of RCB activities.