RESIM 2018 will be the 12th workshop in a series of successful events held on the topic of rare-event simulation since 1997. The topics of the workshop covers all aspects of rare-event simulation, from purely theoretical developments to practical applications. The objective is to bring together researchers, not only from the mathematical sciences, and practitioners to discuss recent results and how methods and open problems from different areas can lead to new directions that drive the field forward. Because of the interdisciplinary nature of the topic, a goal of the workshop is to enhance the interaction between experts in theoretical developments on the one hand, and experts from different application areas on the other. This will be reflected in the plenary talks as well as the invited and contributed sessions, where the aim is to have as diverse a program as possible.