In the Soviet Union theatre was an arena for cultural transformation. This article focuses on theatre director Les Kurbas’ 1929 production of playwright Mykola Kulish’s Myna Mazailo, a dark comedy about Ukrainianization, to show the construction of “Soviet Ukrainian” culture. While the Ukrainian and the Soviet are often considered in opposition, this article takes the culture of the Ukrainian Soviet Socialist Republic seriously as a category. Well before Stalin’s infamous adage “national in form and socialist in content,” artists like Kulish and Kurbas were engaged in making art that was not “Ukrainian” in a generic Soviet mold, or “Soviet” art in a generic “Ukrainian” mold, but rather art of an entirely new category: Soviet Ukrainian. Far from a mere mouthpiece for state propaganda, early Soviet theatre offered a space for creating new values, social hierarchies, and worldviews. More broadly, this article argues that Soviet nationality policy was not only imposed from above, but also worked out on the stages of the republic by artists, officials, and audiences alike. Tracing productions of Myna Mazailo into the post-Soviet period, moreover, reveals a lingering ambiguity over the content of culture in contemporary Ukraine. The state may no longer sponsor cultural construction, but theater remains a space of cultural contestation.