Stimulant use disorders are highly prevalent around the world. Stimulant drugs such as cocaine, methamphetamine, and prescription stimulants create euphoric experiences for users and initiate neurochemical and neuroanatomical processes that can lead to addiction. The pleasant effects of intoxication can be followed by an intensely unpleasant period of withdrawal, where depressed mood, fatigue, and insomnia are common. A stimulant use disorder can be diagnosed when criteria related to substance use and substance-seeking, including distress and/or impairment in functioning, are met. Stimulant use disorders can be accompanied by a wide range of serious medical complications affecting virtually every body system, including myocardial infarction, stroke, kidney injury, infectious disease transmission, and pulmonary disease. Similarly, a wide range of serious psychiatric symptoms can emerge, including stimulant-induced psychosis. Stimulant users are also at a much higher risk of suicide than the general population. This chapter highlights the epidemiology, neurobiology, and varied clinical presentations of this complex group of disorders.