The present research has been conducted using a qualitative method and the technique of reviewing library texts and documents, with the aim of explicating and comparing the nature of the theory of Wilāyat al-Faqīh (Guardianship of the Jurist) in the era of Constitutionalism and the Islamic Revolution. The main question is: How do the viewpoints of ‘Allāmah Muḥammad Ḥusayn Nā’īnī and Imām Khumaynī differ? In response, it must be said that the main difference in the discursive analysis of the principle of Wilāyat al-Faqīh from the perspective of ‘Allāmah Nā’īnī and Imām Khumaynī lies in the type of establishment of justice. Based on this, ‘Allāmah Nā’īnī believes that by limiting the Salṭanah (Sultanate/Monarchy) and establishing a Mashrūṭah (Constitutional) government, one can take steps toward establishing justice in society, whereas Imām Khumaynī believes that establishing justice in society is feasible only through the fall of the Salṭanah and the creation of an Islamic government. One of the most important elements and concepts in the political language of Islām is the element of Wilāyat al-Faqīh; the efficacy of this element in giving identity to the discourse of political Islām in Iran is undeniable. In contemporary political thought, some Fuqahā (jurists) such as ‘Allāmah Nā’īnī and Imām Khumaynī have paid attention to the principle of Wilāyat al-Faqīh, and ultimately, we witness two major viewpoints in two periods of time. ‘Allāmah Nā’īnī, while accepting the Wilāyat of the Faqīh and their supervision over laws, seeks to create a Mashrūṭah government in Iran so that by limiting the monarchy, we witness the establishment of justice in society; whereas Imām Khumaynī, by presenting the theory of Wilāyat al-Faqīh, seeks to create an Islamic government and overthrow the institution of Salṭanah, so that under the shadow of a new model of governance, justice is established in society. In fact, Imām Khumaynī's view regarding the Islamic government is realized in practice. The difference between the Imām and the view of contemporary Fuqahā was that contemporary Fuqahā considered the condition of "probability of influence" to be negated, therefore, they deemed the duty to be waived, whereas Imām Khumaynī did not consider the condition of probability of influence to be negated and, with his high ambition, engaged in paving the ground for the probability of influences and succeeded in creating an Islamic government in Iran.