Iran has many Shiite religious attractions which has made it unique among the Islamic tourism destinations of the world. This chapter examines religious tourism of Iran through a systematic approach, by taking into consideration the dimensions of supply, demand, and effects, but with a focuses on Islam. From the main religions of the world, Islam is the dominant religion of Iran and three religions—Zoroastrian, Judaism, and Christianity—are recognized in Iran as minority religions. Religion is an element of cultural tourism and religious tourism is a common form of tourism in developing countries. Pilgrimage is the main form of religious tourism in Iran and is focused on Shiite pilgrimages primarily to Mashhad as the most important pilgrimage center of Islam after Mecca and secondly to Qom, as the center of Shia religious scholarship and theology and home to some of the country's most influential clerics.