For improving the stability and load carrying capacity of weak subgrade, strengthening methods are to be followed in the field. Among the various approaches, geocells have been identified as an effective soil reinforcement technique for improving soft subgrade behaviour. The three-dimensional honeycomb structure of geocell offers more lateral confinement to the infill soil resulting in improved load carrying capacity. This led to the widespread use of geocells for different geotechnical applications like pavements, foundations, embankments, slope protection, erosion control etc. Many researchers in the past have confirmed the suitability of geocell reinforcement through their experimental, numerical and field studies. In this paper, a comprehensive review of the reinforcement mechanisms, design aspect and numerical modelling techniques of geocell reinforced soil is provided. In addition, this paper highlights the various field application scenarios where different types of geocells have been used and explores the research challenges and scope for further research in this field.