On account of their practically unchallenged status as guardians of objective knowledge, dictionaries are influential elements of societal discourses. They are thus an authoritarian producer and reproducer of societal norms and ideas, and as an interesting object of investigation in critical lexicography consequently lend themselves to the investigation of authoritarian and normalising societal discourses on specific themes. However, dictionaries have to date only been used as primary sources for critical analysis on rare occasions. This study is an attempt at a corrective which explores the presentation of Islam in three editions of the Duden German Universal Dictionary (Deutsches Universalwörterbuch). The dictionaries studied present Islam to all intents and purposes as the Other. Christianity is established as a norm and the Self, and the Christian way of practising religion is depicted as prototypical for all other religions. However, the emphasis on Christianity and the exclusion of Islam also has a positive effect on the portrayal of Islam, as old prejudices on the alleged brutality of Islam are thus not reproduced.