The concept of the soul is very important to be studied in depth, because the soul or nafs is the most important element of the human being, which currently has many problems in its treatment. Because, psychotherapy developed through increasing human potential by increasing happiness turns out to only focus on aspects of the mind and emotions, without touching the deeper dimensions of the human soul. This research aims to analyze the concept of sa'ādah (happiness) according to al-Ghāzalī and compare it with the concept of well-being proposed by Martin Seligman, a contemporary positive psychology figure. The urgency of this study lies in the effort to understand whether the concept of happiness (well-being) through human self-improvement called positive emotion by Seligman has reached the essence of the soul as described by al-Ghāzalī. This research uses a comparative analysis method with a qualitative approach, examining al�Ghazālī's thoughts on sa'ādah and Martin Seligman's concept of well-being in depth. Primary data sources are taken from the main works of both figures, such as Kimya al-Sa'ādah by al-Ghāzalī and flourish: Flourish: A visionary new understanding of happiness and well-being. by Seligman, as well as several other relevant works. Secondary sources include journal articles and scientific works from scholars who discuss the thoughts of the two figures. Data analysis is conducted through content analysis and comparative analysis techniques to reveal the similarities, differences, and implications of the two concepts. The results showed three main findings. First, Seligman explains that happiness (well-being) can be achieved by cultivating positive emotions and performing actions that benefit others. Second, al-Ghazālī distinguishes happiness into two types: temporary happiness related to the fulfillment of bodily needs, and ultimate happiness which is eternal through ma'rifatullah (knowledge of Allah). This ultimate happiness is the highest level achieved through the purity of the soul. Third, there are significant similarities and differences between the thoughts of Seligman and al-Ghāzalī. Both discuss the concept of happiness that is worldly ortemporal, while al-Ghāzalī formulates his concept based on an in-depth analysis of the Qur'an, which includes the concept of spirit and soul. The implication of this research is a more comprehensive understanding of the limitations of Seligman's positive psychology concept that focuses on the symptoms of the soul, not on its substance. In addition, this research opens up opportunities to reformulate al-Ghazālī's metaphysical concept of the soul into a psychotherapeutic approach that is more scientific and relevant to the modern context. This research is expected to make a significant contribution to the development of Islamic psychology and bridge the gap between Western psychology and classical Islamic thought on happiness and mental well-being.