Since the inception of the modern State, built on the concepts of representative government and of separation of sovereign powers, parliaments have been in charge, either solely or concurrently, of exercising one of the most important functions of state sovereignty - the legislative function. As institutions that derive their political legitimacy directly from their elected composition, parliaments insure, or at least inspire, that legislation they enact is based on a solid democratic and pluralistic basis. Evidently, where one finds the legislative power, one also fins legislative procedure, and, where it all starts, legislative initiative. This dissertation's aim is to study legislative initiative from a comparative perspective, looking at it as ideal legal type that transcends borders and functions as common denominator within the several legal systems, in the guise of trying to achieve, as result of our research, a thorough definition of legislative initiative as an abstract legal concept detached from national idiosyncrasies and topical characteristics. As such, the dissertation's comparative research has demonstrated legislative initiative to be a procedural right bestowed by the constitutional order on a select few political actors enabling them to put forward a demand of normativization of their political options, as means of transition from the policy-making stage into the rule-making stage. Through the presentation of a legislative proposal, the holders of the right of legislative initiative are allowed to select the subject of legiferation and its scope and to request from the parliamentary assembly to which it is addressed the production of a legislative decision on the submitted proposal. All parliamentary activity subsequent to the presentation of a legislative proposal is modelled and conditioned by the proponent's selection of subject and scope. Therefore, it is proposed, the right of legislative initiative is directly at the cause or source of statutory enacted legal norms.