An efficient and successful electrochemical process must take place in an electrochemical reactor with an adapted and optimized design that allows superior performance to be achieved. Traditional manufacturing methods have made the task of optimizing and adapting reactors very expensive. However, 3D printing allows prototypes to be built in a very short time and at a very low cost compared to traditional manufacturing techniques. This has caused research into new electrochemical reactors in different laboratories to skyrocket in recent years. The rapid evolution of 3D printing technology, as well as the appearance of new materials, have meant that they can be included in many applications, such as the electrochemical treatment of contaminated water or energy devices, batteries or fuel cells. In this review, the latest advances in the manufacture of electrochemical reactors and the main applications that have made use of them will be presented and critically discussed.