Membrane-based air dehumidification (MAD), a recently emerged air dehumidification technology, separates the moisture from the humid air by using a selective membrane. MAD is carried out by permitting only vapour molecules to transfer from one side of the membrane at a high concentration to the other side at a low concentration. The MAD process has superior performance translating to favourable energy and economic benefits than other traditional dehumidification technologies. This chapter comprehensively reviews the literature on MAD including membrane characteristics, membrane configuration, membrane-related mass transport mechanism, and system design and operation as well as the mass transfer modelling. State-of–the-art developments in MAD are presented and finally recommendations on future research directions are provided. This chapter provides a comprehensive discussion of the MAD technology including membrane materials, thermophysical characterization, membrane forms and modules, system configurations, and mass transport modelling.