Digital Health Twins (DHTs) represent a groundbreaking advancement in personalized and predictive healthcare, functioning as real-time, data-driven digital replicas of individual patients. By integrating continuous physiological, behavioral, and contextual data from sources such as wearable devices, biosensors, electronic health records (EHRs), and mobile health platforms, DHTs simulate the progression of health conditions, predict outcomes, and enable individualized care planning. This systematic literature review investigates the current landscape of DHT development and implementation with a specific focus on their clinical, technological, ethical, and organizational dimensions. The review followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) 2020 guidelines, ensuring transparency, reproducibility, and methodological rigor. A total of 72 peer-reviewed journal articles published between 2010 and 2022 were selected from five major databases, representing diverse disciplines including biomedical engineering, health informatics, artificial intelligence, and occupational health. The findings indicate that DHTs are being widely utilized for early detection of chronic diseases, personalized risk profiling, and virtual treatment simulations, particularly in specialties such as cardiology, oncology, and neurology. In parallel, DHTs are enabling a new era of personal health management through real-time biofeedback, digital coaching, and self-monitoring tools that empower individuals to make data-informed lifestyle decisions. The review also reveals emerging applications of DHTs in corporate health and workforce wellbeing, where they support occupational health surveillance, wellness program optimization, and predictive modeling of employee engagement and absenteeism. This review not only consolidates current knowledge across multiple sectors but also identifies critical research and policy gaps, highlighting the need for robust ethical frameworks, standardized interoperability protocols, and inclusive governance mechanisms to ensure the equitable and responsible implementation of DHTs across healthcare ecosystems.