We are all aware of sexual orientation and its influence on sexual behavior, but the true nature of this complex occurrence is elusive. Despite extensive investigations there is no clear answer as to what sexual orientation is. Conjectures far outweigh proven fact. Based on extensive experience counselling clients regarding sexual orientation issues, such as discrimination and persecution, it became apparent that common perspectives are inaccurate. A major problem pertains to how theories of sexual orientation are generated, without first establishing criteria for a robust theory. Correcting this error, twelve comprehensive criteria for a robust theory of sexual orientation are presented. Major biological, evolutionary, and psychosocial perspectives are evaluated based on the theory criteria, revealing weak performance. With the goal of aligning clinical and research realities, and guided by the twelve theory criteria, a four-component approach—homoerotic and heteroerotic dimensions, activation/deactivation of these dimensions, erotic fantasy, and social construction—that comprehensively define sexual orientation, is proposed. This proposition represents the first novel theory of sexual orientation in decades, explaining many fascinating sexual orientation occurrences. It is a must read for researchers/scholars, graduate/undergraduate students, and sexual orientation counsellors.