Biography texts of the early 19th and early 20th centuries, where the printing press culture was not fully internalized in the Ottoman Empire, but also allowed to discuss the transition from oral culture to written culture, are among the important sources that reflect the society's view of insanity with the information they contain on the subject of "insanity". However, the concept of "madness" in Turkish folklore studies has not been discussed much from the biography texts until now. It is necessary to think about the question of how the poets, who were called "crazy" in the last period of the Ottoman Empire, were perceived in the society, based on the saying "Every community has its own folklore", and the fact that educated poets belonging to the city culture and belonging to the upper class are a group. One of the issues to be addressed within the framework of Ottoman cultural history is the ways in which the concept of insanity was comprehended in the Ottoman society. The comprehension of the concept of insanity from the late 19th century to the early 20th may be discussed by means of the biographies of poets who were mentally unwell in real life. Son Asır Türk Şairleri discusses poets who, for various reasons, had lost their mental health and who displayed abnormal behavior, and, at the same time, portrays how some of these poets had been foregrounded not by their mental illnesses but by their anomalous characters. Moreover, these figures are referred to in the collection of biographies through various forms of naming, such as crazy [deli], lunatic [mecnun], and mad [meczup]. This study aims to address the following questions: What are the incident leading to anomalous character traits among the poets whose biographies are included in the collection? What are the distinguishing elements of the process by which these mentally unwell poets are called crazy, lunatic, or mad? Could this naming process be discussed in the framework of "romantic," "intelligent," or "sacred" insanity? It is observed that, in the Ottoman society, mentally unwell people were subject to various practices depending on the severity of their illness, and that they mostly led daily lives in interaction with other people without being alienated from public space. Michael W. Dols categorizes insanity in three groups as "romantic," "intelligent," and "sacred" insanity. When the biographies included in Son Asır Türk Şairleri are analyzed, it becomes evident that types of insanity cannot be easily distinguished as in Dols's categorization. It is evident that a person considered a "romantic" lunatic may as well possess characteristics of "intelligent" and "sacred" insanity. It is also notable that, in the collection, "romantic" insanity and "intelligent" insanity are demonstrated as coexisting, and so are "intelligent" insanity and "sacred" insanity. In addition, the collection points to some mentally unwell poets who had lost their mental health later, as an outcome of the major traumas they had experienced. While the reasons for losing their mental health may have been familial, social, and political factors, they may also be related to the effect of literary texts. The fact that the Mecnun [lunatic] type, in literary texts, constitutes a model for the identity of one who is in love has motivated poets into acting like they were Mecnun [lunatic]. Having isolated themselves from the society by centering their lives on love, these poets resisted all forms of authority that they came across. The poets who introduced criticisms opposing those in power, in line with the period's political atmosphere, were also deemed insane as they were repugnant. What is more, although they were not insane, they were disguised as such and admitted to insane asylums by their relatives so that they would not be convicted for their critique of the government. Consuming alcohol, too, was regarded as a reason for insanity, and poets addicted to alcohol are presented to the reader as a didactic lesson since their lives ended tragically due to not using their intellect "in the right way." Those who were maddened by their love of God, however, were accepted to demonstrate abnormal behavior in social life, and they were even thought of as messengers from the realm of obscurity, thereby being worthy of a saintly status. The fact that they did not conform to social rules and fulfill their religious duties, and that they depicted abnormal behavior and were addicted to alcohol was not deemed odd. [ABSTRACT FROM AUTHOR]