Scholars have generally treated the abstract painter Frank Stella as a quintessential American artist, whose late modernist canvases catalyzed postwar American art. Yet such accounts gloss over Stella’s significant experiences of international travel, including a formative trip to Iran in 1963, made possible by the expansion of U.S. global power after World War II. Drawing on unpublished photographs, letters, and drawings from his trip, I argue that some of the artist’s most significant formal innovations of the 1960s were a direct result of his encounter with Iranian Islamic architecture. Specifically, I trace connections between the Irregular Polygons, a series of forty-four paintings Stella produced between 1965 and 1967, and the Qur’anic epigraphy he documented at Sultaniyya, a fourteenth-century Ilkhanid mausoleum in northwest Iran. “Islamic Architecture in New York Painting” opens up new geographic terrain in the history of American art while insisting on the significance of U.S. global expansionism to its canon. © 2022 Smithsonian Institution Published by the University of Chicago Press.