Sodium–potassium adenosine triphosphatase (Na+/K+-ATPase) is an enzyme located in the plasma membrane of most eukaryotic cells, responsible for maintaining ion concentration gradients against their concentration scale using ATP hydrolysis as a source of energy. The enzyme is involved in many cellular activities, including maintaining cell volume, transporting nutrition, electrical potential, neurotransmission, and any dysfunction or modification of enzyme activity is directly linked to many diseases, such as epilepsy, cardiovascular disease and hypertension, diabetes and other metabolic disorders, digoxin toxicity, fetal abnormalities, neurological disorders, and pulmonary conditions. In this book, the authors present current research on regulation strategies, Na⁺/K⁺-ATPase as a biomarker in diseased states, and the use of Na⁺/K⁺-ATPase in the physiological and ecological adaptations of insects. Other topics discussed in this compilation include the effects of hormonal and non-hormonal stimulation on Na+/K+-ATPase activity, the physiology and pathophysiology of Na+/K+-ATPase, Na⁺/K⁺-ATPase as a biomarker for energy metabolism and oxidative stress in diseased states, the neurotensin inhibitory effects of [3H]-Ouabain binding to striatal membranes and inversion by administration of clozapine, and Na+/K+-ATPase’s important functional roles in human body.