The article mobilizes the concepts of “canon” and “canonization” to discuss John Williams’s legacy. It sets the scene by providing an overview of the most noted formulations of “canon”—from Joseph Kerman’s 1983 articulation to the most recent revisions by Mark Everist and William Weber—and of the most noted controversies and debates around it. The invocation of such unstable and problematic concept is warranted by the deep roots that the film music of the classical Hollywood had in the nineteenth-century operatic and symphonic tradition, a tradition that also included, in its aesthetic and philosophical tenets, the very concepts of canon and canonization. In turn, the film music of John Williams is deeply rooted in the tradition of the film music of the classical Hollywood and hence, for transitive properties, also in the aforementioned nineteenth-century musical and aesthetic traditions. Specifically, the concepts of “canon” and “canonization” are applied to Williams’s work by considering the composer’s importance in relation not only to the “Hollywood music canon” but also to the “art music canon” of Western music. Williams has arguably worked within a tripartite set of canons: his film scores have been referencing past canonical works consistently, not in an uninventive plagiaristic manner but in a productive paraphrasing one, as most conclusively demonstrated by James Orosz in 2015. In such a canonizing function, Williams has been long praised as a sort of herald of symphonic music—particularly a brand of updated late-Romantic symphonism, which he has called “Romantic atonalism”—an advocate who could bridge the gap between “art music” and the masses and keep the influence of the “long nineteenth century” still relevant in today’s music. Second, he has been instrumental in the canonization of the past Hollywood music, not only in reviving that style, which was considered dead and buried in the late 1960s when Williams was consolidating his credentials in the film industry. Williams has also been instrumental in igniting an interest for the past music of Hollywood in the record market and on the concert stages, particularly with his parallel career as a concert conductor. Third, as the current dean of film music, Williams has been himself the object of a process of canonization, becoming the point of reference for those who wish to keep symphonic film scoring alive, but also for concert composers who have found in Williams’s idiom a source of inspiration. John Williams has been an important figure both as a canonizing revivalist and as a canonized model.