This study looks at the Islamic character of the Acehnese state in the seventeenth century. It examines not only its Islamic institutions but also its political culture and policies towards Islam. The discussion begins with a historical sketch of the rise of Aceh in the sixteenth century, followed by an analysis of the ruler and authority, the royal enclosure, Islamic religious ceremonies and the Islamic institutions of the state. The work concludes with a brief comparison of Aceh with other Islamic states in the region, especially Melaka and Mataram, whereby it is shown that the Islamic nature of the Acehnese state was more pronounced. This study is of particular interest to scholars and students of Islam, history, anthropology and political science.