The main objective of this book is to simplify the abstract concepts of nursing theories and accelerate the application of these theories into nursing practice, nursing education and nursing research thereby improving the quality of nursing care., This book focuses on the concepts of various nursing theories and application of these theories into nursing with a case scenario. This book is divided into three units. Unit I: Introduction to Nursing Theories illustrates the terminologies, evolution and types of nursing theories and how it can be used in nursing practice. Unit II: Grand Nursing Theories provides illustration of fourteen nursing grand theories along with its application. Finally, Unit III: Middle-Range Nursing Theories focuses on the sixteen middle-range nursing theories. Each chapter covers a detailed description of a theory categorized under biography of the author, assumptions, major concepts, metaparadigm in nursing, application into nursing education, practice and research, nursing process, case scenario and critique of the theory.