The study aims to examine the risâlah called Risâlat Ithbât al-wâcib, which belongs to Huseynî al-Halhâlî (d. 1014/1605). In the study, it is aimed to analyze this treatise of Huseynî al-Halhâlî, which has not been studied, and to be brought to the literatüre of the history of Islamic thought. In line with these determined targets, the study covers the life of author, the copies of treatise and problems that the treatise is related to. His work Risâlat Ithbât al-wâcib deals with the proof of the existence and unity of God and his attributes and actions. This treatise of Halhâlî is similar in terms of content and method to Jalâl al-Dîn al-Dawânî’s Risâlat Ithbât al-Wâjib al-jadîda and Sadr al-Dîn al-Dashtakî’s Risâla fî Ithbât al-Wajib wa-sifâtihî. In fact, this treatise is the annotation of al-Dawânî’s Risâlat Ithbât al-Wâjib al-qadîma in some library cataloques; and in some, this treatise is the annotation of al-Dawânî’s Risâlat Ithbât al-Wâjib al-jadîda. However, the relationship between this treatise of Halhâlî and both of al-Dawânî’s work is in terms of the problems it contains. This treatise of Halhâlî has a remarkable quality in terms of the subjects it deals with in the Works titled Ithbât al-Wâjib which were written in the period of Islamic thougt tradition.