This contribution commemorates Oliver Williamson, who recently passed away, as one of the founding fathers of Transaction Cost Economics (TCE). It does so by touching on some of the details of his personal life and connecting these with his professional career. The latter was devoted to putting the study of institutions on the economic agenda. Closer scrutiny reveals that three phases may be identified. Williamson first developed an interest in analysing vertical integration. During the second phase, he elaborated this interest in TCE, and during the third, he positioned his contributions within the area of institutional economics. Furthermore, the article considers the various influences of institutional and organizational economists on Williamson. Finally, the article considers the reception, criticism, and further elaborations of Williamson's contributions.