The overarching research problem of this dissertation is to account for the historical emergence of Hawaii's interracial working class, focusing on the islands' three most important industries---sugar, pineapple, and stevedoring---primarily from the 1920s to the early 1950s. Up until World War II, Hawaii's workers were deeply divided racially: if and when they organized, they did so on racially exclusive bases. Then, seemingly overnight, toward the end of the war, the workers organized themselves into one large, left-led union and engaged in a consciously interracial class struggle. This study proffers a multi-layered explanation which, inter alia, contravenes the predominant view that interracial working-class formation was a deracializing process. First, confronted with inconsistencies and ambiguities in the prevailing objectivist theories of race and class, the study asserts an alternative explanation for the prewar racial divisions among the workers. It demonstrates that Portuguese, Japanese, and Filipino workers---the vast majority of the work force---faced distinct racisms based on fundamentally different assumptions, which shaped their divergent and conflicting politics. Second, since workers tend to conceptually define themselves as a class in the face of vigorous employer opposition, the study examines the origins of the employers' long-standing hostility and finds the employers' capacity for organization to have been pivotal. Third, the study argues that the following conditions facilitated the genesis and phenomenal growth of the interracial working-class movement: expansions in political opportunity, largely via national state intervention; an increase in the workers' organizational capacities via their growing ties to mainland workers as well as among themselves; wartime martial law's fomenting of worker discontent; and an erosion of anti-Japanese racism during the war. Fourth, a close examination of the movement's discourse and practices reveals a much more complex interplay of race and class than heretofore assumed. Rather than a colorblind class ideology, a syncretic ideology of race and class---that rendered coincident and mutually reinforcing the workers' struggles for racial and class justice---defined, shaped, and motivated the movement. The study draws on data gathered from various archival collections, oral histories, newspapers, and government documents.