Cancer is not only a biological illness but also a profound psychological and emotional challenge that deeply affects patients and their families. This introductory chapter presents the foundation of psycho-oncology, a multidisciplinary field that recognizes and addresses the complex emotional, behavioral, and cognitive aspects of cancer. Emphasizing the psychological distress associated with diagnosis and treatment—such as anxiety, depression, trauma, and existential fear—the chapter underscores the importance of integrating evidence-based psychotherapeutic interventions into oncology care. Various therapy models including Cognitive Behavioral Therapy (CBT), Acceptance and Commitment Therapy (ACT), Mindfulness-Based Stress Reduction (MBSR), EMDR, Schema Therapy, and others are introduced, along with their proven benefits in enhancing emotional resilience and quality of life. Additionally, the chapter highlights the role of family and social support, the concept of posttraumatic growth (PTG), and the expanding role of digital and AI-assisted interventions in improving access and personalization of psychological care. Overall, this chapter sets the stage for a holistic, integrative, and person-centered approach to cancer treatment.