Substantial inequities in cancer care persist across countries and population groups with lower levels of human development. Although very high- and high-Human Development Index (HDI) settings often report higher cancer incidence and comparatively lower mortality, low- and medium-HDI countries experience lower recorded incidence but disproportionately higher mortality-to-incidence ratios. This pattern reflects delayed diagnosis, restricted access to treatment, workforce shortages, and fragile health systems. This narrative policy paper examines how oncology nurses can contribute to reducing these inequities across the cancer care continuum in low- and medium-HDI settings. Drawing on evidence from nursing practice, health systems research, and cancer control initiatives, we emphasize the roles of oncology nurses in prevention, early detection, treatment, survivorship, and palliative care. Key contributions include health education, community-based screening, patient navigation, symptom management, psychosocial support, and culturally responsive end-of-life care. The paper also discusses innovative and scalable service-delivery models, including task-sharing approaches, nurse-led early detection initiatives, case management, telemedicine, and international capacity-building partnerships. Despite their strategic importance, oncology nurses remain constrained by limited access to specialized education, inadequate policy recognition, workforce shortages, burnout, and insufficient locally generated evidence. Addressing these barriers requires sustained investment in oncology nursing education, leadership development, research capacity, and supportive health policies. Strengthening oncology nursing is therefore a practical and potentially high-impact strategy for expanding access to care, improving service continuity, and advancing cancer care equity in resource-constrained settings.