Nursing theory is defined as "a creative and conscientious structuring of ideas that project a tentative, purposeful, and systematic view of phenomena". It is an organized framework of concepts and purposes designed to guide the practice of nursing. Nursing theories provide a way to define nursing as a unique discipline that is separate from other disciplines, such as medicine. They are essential to the care of patients and provide a foundation for nursing practice.

Nursing theories are generally categorized into three different levels: grand nursing theories, mid-range nursing theories, and nursing practice theories. Grand nursing theories are based on broad, abstract, and complex concepts, while mid-range nursing theories drill down into specific areas of nursing rather than deal with sweeping concepts. Nursing practice theories are more specific and focus on the practical aspects of nursing care.

Nursing theories help guide and define nursing care and provide a foundation for clinical decision-making. They provide nurses with rationale in patient care and help to define the different particular contribution of nursing with the care of clients. Nursing theories also administer a structure for communicating with other nurses and with other representatives and members of the healthcare team. They help nurses use critical thinking skills, analytical skills, and improve concept comprehension.

Nursing theories are a relatively new component of the nursing profession. Despite their recent appearance, nursing theories have made a strong and lasting impact on the education, training, and development of professional nurses. They have also influenced patient care and outcomes in everyday nursing practice.