The dramatic salience of university rankings is usually attributed to a number of macro-level trends, such as neoliberal ideology, the spread of audit culture, and globalization in the broadest sense. We propose that the institutionalization of university rankings cannot be fully accounted for without a better understanding of the meso-level processes that enable it. To explore these, we zoom in on an organization called IREG Observatory (whereby IREG stands for 'International Ranking Expert Group'). Since it first emerged, in 2002, IREG has acted as a carrier of a kind of rationalized 'faith in rankings'--a faith it has laboured to justify, diffuse, and solidify through boundary work at the intersection of technocratic, managerial, academic, and commercial spheres. Drawing on the insights gained from this particular case, the article argues that the institutionalization of university rankings is not solely a matter of universities being impelled by them but also a matter of how actors in and around the university sector collectively partake in the legitimation of the practice of ranking universities. At a more general level, our analysis potentially provides a blueprint for understanding boundary work as a meso-level process that plays an important role in the institutionalization of rankings, and other devices of evaluation.