Modelling and simulation are well-established tools for investigating the physical processes inside a polymer electrolyte membrane (PEM) fuel cell. The early literature paid great attention to steady-state transport phenomena in the main components, which continues to be a focus of ongoing activities. There is, on the other hand, a growing interest in modelling other aspects of fuel cell operation, such as transient performance and degradation phenomena. There has also been a growth in the number of molecular and pore-level studies of transport phenomena in fuel cell components, enabled by developments in simulation techniques and enhancements in computer hardware. Such approaches are capable of representing important small-scale phenomena more faithfully than traditional macroscopic models. This review summarises recent activity in PEM fuel cell modelling, with a focus on detailed physical models, and considers its potential significance. An industrial perspective is also provided, highlighting the current use of modelling in the test and design cycles, and outlining future requirements.