All individuals have to deal with health and illness.  Their health behavior can directly impact their health outcomes. Engaging in healthy behaviors reduces the risk of certain conditions, while unhealthy behaviors can increase that risk. Health behaviors encompass overt behavioral patterns, actions, and habits that relate to maintaining, restoring, and improving health (Gochman, 1997: 3). This definition includes various behaviors such as diet, alcohol use, smoking, physical activity, sexual behaviors, medication adherence, screening, and vaccination. Examining health behaviors in both healthy and health-compromised populations is a crucial area where public health has made significant contributions to improving people's well-being. Health literacy is closely related to health behavior and refers to a complex network of knowledge and skills that empower individuals to educate themselves and be educated (Nutbeam, 2008; Sørensen et al., 2012). Nutbeam (2008: 2072) defines health literacy as "the extent to which individuals have the capacity to access, process, and understand basic health information and services needed to make appropriate health decisions." Individuals with limited health literacy often struggle to navigate the healthcare system, especially when it comes to accessing preventive care, screenings, diagnoses, and treatments. McCaffery et al. (2010) argue that low health literacy occurs when a person's literacy and numeracy skills do not align with the often technical, complex, and unfamiliar information provided by healthcare professionals and organizations. To improve people's health behavior, health promotion is necessary. Health promotion is the process by which individuals increase control over and enhance their health (WHO, 1986). Numerous health promotion programs and interventions have been developed to improve the health and well-being of individuals and groups. These interventions aim to shift the focus of healthcare from hospitals to community-based settings (Baxter et al., 2018). This Handbook consolidates essential knowledge on health behavior, health literacy, health education, health promotion, and programs/interventions that can enhance global health. It is divided into two books and several parts covering health disciplines, theories, concepts in health behavior, health promotion, and illness prevention. Book one will contain specific sections that address health behavior, health literacy and education, health environment.  Book two will embrace theoretical aspects of health promotion, health programs and interventions for promoting health, and research methods applicable to examining health behavior and illness prevention in individuals and groups. Chapters in both books encompass both theoretical and practical aspects of health behavior and illness prevention. The Handbook takes a critical perspective when addressing these issues and avoids adopting a deficit model or victim-blaming approach. For instance, health-compromising behavior may stem from low health literacy, which could, in turn, result from a lack of education. However, the Handbook seeks to delve into the underlying causes of individuals' lack of education, which may be linked to marginalization, poverty, power imbalances, and similar factors. By avoiding a deficit model or victim-blaming approach, the chapters in the handbook will tackle the root causes of health-compromising behavior. Contributors to the Handbook include researchers and practitioners specializing in health behavior and health promotion. Their work contributes to illness prevention and the improvement of health and well-being in individuals and groups. The chapters will be valuable to students, researchers, and practitioners in the health fields.