The vagus nerve is one of the most important, yet most under-appreciated structures of the human body. It is the tenth cranial nerve innervating many of the visceral structures of the human body. It has been called the "wandering" nerve, given its ubiquitous and meandering course throughout the body. The major branch of the parasympathetic nervous system, it optimizes the body's state of rest, relaxation and recovery and is necessary to optimize health. It is a counterbalance to the sympathetic nervous system, which regulates the body's fight or flight response. Containing over 160,000 fibers, it has both afferent and efferent branches, providing information to the brain on the status of the body's organs. The brain then sends signals back down the vagus nerve to optimize bodily functions. Vagus nerve stimulation is a new frontier in medicine, tapping into the body's intrinsic capability to optimize an organ's function, control systemic inflammation and modify diseases without drugs. The use of non-implanted vagus nerve stimulators has made it possible to move neuromodulation up the treatment continuum, and has facilitated access for clinical evaluation and treatment. Scientists now have the ability to translate the basic science into clinical practice without the need for surgical intervention. Vagus Nerve Stimulation serves as a compendium of current knowledge about stimulating the vagus nerve in many different disease states. Chapters include applications to neurologic conditions, psychiatric conditions, inflammatory conditions, metabolic disease, reperfusion injuries, long covid, cardiac disease and even optimizing performance in healthy individuals.