End-of-life care in the intensive care unit (ICU) represents one of the most ethically complex areas of contemporary healthcare. Advances in life-sustaining technologies have increased the ability to support failing organs, but they have also created difficult decisions concerning treatment limitations, patient autonomy, medical futility, surrogate decision-making and the appropriate transition from curative treatment to comfort-focused care. Critical care nurses occupy a central position in these situations because of their continuous bedside presence, close relationships with patients and families, and responsibility for symptom assessment, communication, advocacy and the implementation of care plans. This narrative review examines the principal ethical challenges encountered during ICU end-of-life care and explores the professional responsibilities of critical care nurses in promoting dignity, comfort and ethically defensible decision-making. The discussion addresses autonomy, beneficence, non-maleficence, justice, withholding and withdrawal of life-sustaining treatment, advance care planning, informed consent, family conflict, cultural and spiritual diversity, palliative sedation, resource allocation and moral distress among nurses. Evidence from professional guidelines, systematic reviews, consensus statements and relevant ethical literature published through 2025 was considered to develop an integrated overview of clinical practice. The literature emphasises the importance of shared decision-making, transparent communication, interdisciplinary collaboration, timely palliative care, appropriate symptom management and respect for patients' values. Critical care nurses can facilitate these processes by recognising unmet palliative needs, supporting patients and families, documenting concerns, participating in ethical discussions and advocating for patient-centred care. Nevertheless, their effectiveness may be limited by hierarchical decision-making, inadequate training, staffing constraints and emotional exhaustion. Strengthening ethics education, communication skills, institutional policies and staff-support systems is essential to improving the quality of end-of-life care in critical care environments.