The accusation of “ghuluww” (“excess”, “exaggeration”, sometimes “extremism”) is one of the earlier polemical devices of the Islamic tradition, as it is mentioned twice in the Qur’ān (4:171 ; 5:77) in the context of anti-Christian polemics. However, it is in the domain of intra-Islamic polemics that it gained currency. The accusation found its most important development in the works of 3rd/9th century theologians and heresiographers who used it against certain branches of the Shīʿa which they subsumed under the derogatory label of Ghulāt (or “al-ghāliya”). The accusation aimed at specific Shīʿī groups holding various esoteric doctrines denounced by theologians (both Shīʿīs and non-Shīʿīs) as "exaggerate", such as the divinity of the Imām, the transmigration of souls, antinomianism, etc. Some theologians went as far as to proclaim the expulsion of groups labelled as Ghulāt from the Islamic community. However, early mentions of the accusation “ghuluww” in polemical epistles from the 1st-2nd/7-8th centuries and lexicographical treatises from the 2nd/8th and early 3rd/9th centuries show that it was originally used against the Khawārij rather than the Shīʿī groups which later came to be widely known as Ghulāt. The accusation aimed at what polemicists deemed a schismatic attitude of the Khawārij, purportedly leading them to adopt an excessively restrictive definition of the Islamic community and to exclude their opponents from it. Moreover, we find traces of this early definition of “ghuluww” as schismatic excess being simultaneously applied to both the Khawārij and branches of the Shīʿa in the works of early 3rd/9th theologians such as al-Jāḥiẓ and Ḍirār b. ʿAmr. In contrast, later sources draw a sharp distinction between these two currents and develop a purely doctrinal definition of “ghuluww” as an excess in esotericism, applying it solely to branches of the Shīʿa while excluding the Khawārij from its range. Through a genealogy of the accusation of “ghuluww” from the 1st-7th to the 4/10th century, this paper therefore engages in a critical study of the development of intra-Islamic polemics and its discursive devices. Furthermore, the confrontation of various definitions of “ghuluww” across time and texts throws a spotlight on the early disputes around the definition of the Islamic community and its shifting boundaries during the formative period. This study also aims to historicize the framework and categories through which classical Islamic sources of the late 3rd/9th and early 4/10th centuries depict the religious and political landscape of early Islam.