The security of the Persian Gulf has long been a subject of scrutiny and concern for regional and global policymakers. Generally, there are two distinct perspectives on regional security in the Persian Gulf: 1) an "external outlook" and 2) an "internal outlook." This study seeks to answer why the concept of security in the region varies across different actors and what implications the role and objectives of extra-regional powers—particularly in defining the concept of security in the Persian Gulf—entail. The study's underlying assumption is that each regional actor interprets the concept of security differently based on its domestic concerns and foreign policies. Another factor contributing to the lack of consensus among regional states is the definition of security itself, as well as the role and objectives of extra-regional powers, such as the United States, in the region. This research employs an analytical-descriptive methodology with a comparative approach, and data collection is based on documentary and library research methods. The theoretical framework of this study revolves around the concept of security, grounded in the Regional Security Complex Theory. The findings indicate that, from an external perspective, security in the Persian Gulf is defined by elements and factors outside the region, whereas the internal perspective emphasizes intra-regional dynamics among Persian Gulf states as the defining factor. Divergent interpretations of security between the two sides of the Gulf (Iran and the Arab littoral states) have led to strained relations and recurrent crises.