Iran’s tumultuous twentieth century witnessed the rise of competing conceptions of nationalism. In the period shortly after World War I, Iranian intelligentsia began to criticize European materialism, and to craft a totalizing spiritual conception of Iran’s national culture. Initially, they emphasized elements of pre-Islamic Zoroastrian culture to supplement a race and language-based nationalism. With the revival of Shi‘i thought in the post WWII period, the search for the spiritual content led to a reassertion of Iran’s Islamic, and in particular, Shi‘i heritage, and the creation of a nationalism first and foremost defined by the Shi‘i identity of the nation. While the ethnic nationalism of earlier decades sought to distance Iran from Arab-Islamic civilization, this emerging Shi‘i nationalism construed “the West” as the enemy of Islam bent on dividing the Islamic world. This external Other, however, now had an internal counterpart. The religious intellectuals of this period identified Iranianness with Shi‘ism, and constructed Iran’s Baha’is as the nation’s internal Other intimately connected with the external enemy. Their religiously defined nationalism was linked with the notion of Shi‘ism as a mobilizing political ideology on the one hand, and the process of politicization of anti-Baha’ism on the other. The latter emerged in the late 1930s with the appearance of The Confessions of Dolgoruki, the forged memoirs of the Russian ambassador to Iran; gained momentum with its widespread publication in the 1940s; and culminated with identifying Baha’is as an instrument of western colonialism bent on fracturing Iran and destroying the religious unity of the country. By the beginning of 1960s, Baha’is had become “the hands of colonialism.” This portrayal of an indigenous religious formation as the internal Other played a fundamental role in the process of constructing an Islamist revolutionary identity and refashioning the political role of the Muslim clergy in a rapidly-crystallizing political project that reached a climax with the Islamic Revolution of 1979. Through an in-depth study of the writings and talks of prominent religious intellectuals of the twentieth century Iran such as Ahmad Fardid, Jalal Al-e-Ahmad, Ali Shariati, Mehdi Bazargan, and Seyyed Hossein Nasr, this paper explores the conception of Shi‘i nationalism in mid-twentieth century Iran and demonstrates its linkage with anti-Baha’ism.