This article is a brief introduction to the rapidly evolving field of many‐body localization. Rather than giving an in‐depth review of the subject, our aspiration here is simply to introduce the problem and its general context, outlining a few directions where notable progress has been achieved in recent years. We hope that this will prepare the readers for the more specialized articles appearing in this dedicated Volume of Annalen der Physik, where these developments are discussed in more detail. Many‐body localization can occur in isolated, interacting quantum systems with strong quenched disorder. Many‐body localized systems are different from the more common ergodic systems in that they fail to reach thermal equilibrium at long times. Instead, these systems are characterized by the absence of transport, similar to non‐interacting Anderson insulators, and have novel dynamical and entanglement properties. This article is a brief overview of the recent theoretical and experimental progress in this active field of research featured in this special volume of Annalen der Physik.