In the study of pedestrian dynamics, the consideration of group behaviours is essential, as group interaction within crowds is a common phenomenon and significantly influences pedestrian behaviours. This special issue highlights the importance of pedestrian group behaviours and examines the subject using a wide range of methods, such as experiments, modelling, and algorithms. The works comprising this special issue can hence provide ideas for future studies on pedestrian dynamics and can also serve as a long-term reference for modelling pedestrian group behaviours.