For many years, the social role of librarians has been a topic of heated debates, both within the library field and within library research. Such debates have traditionally been about questions of neutrality and the professional identity in librarianship. Recently, visions of librarians as radical positive change agents (Lankes 2016) have influenced and shaped this debate, raising new questions about neutrality or “post-neutrality”, professional agency and personal and political ideologies. However, what does it mean to be a radical positive change agent? To expand our understanding of the librarian as a radical positive change agent, this paper introduces the concepts of activism and social entrepreneurship. By highlighting similarities and differences between the concepts of the change agent, the activist and the social entrepreneur, this paper aims to inform future discussions about the proactive role of librarians working for change. The current focus on how librarians should act as agents for change in relation to the UN sustainability agenda and the Sustainable Development Goals (SDGs) serves as an example throughout. The paper concludes by posing questions for further discussions of how the concepts of the change agent, the activist and the social entrepreneur might expand our understanding of the proactive librarian and how they might translate to the practice of librarianship in the era of “post-neutrality”.