Obesity is a major public health concern that leads to numerous metabolic, mechanical and psychological complications. Although lifestyle interventions are the cornerstone of obesity management, subsequent physiological neurohormonal adaptations limit weight loss, strongly favour weight regain and counteract sustained weight loss. A range of effective therapies are therefore needed to manage this chronic relapsing disease. Bariatric surgery delivers substantial, durable weight loss but limited access to care, perceived high risks and costs restrict uptake. Medical devices are uniquely positioned to bridge the gap between more conservative lifestyle intervention and weight-loss pharmacotherapy and more disruptive bariatric surgery. In this Review, we examine the range of gastrointestinal medical devices that are available in clinical practice to treat obesity, as well as those that are in advanced stages of development. We focus on the mechanisms of action as well as the efficacy and safety profiles of these devices. Many of these devices are placed endoscopically, which provides gastroenterologists with exciting opportunities for treatment.