The monograph critically reviews most commonly used geotextile structures, their properties and performance characteristics. In general, both natural and synthetic fibres are used for the production of geotextiles, and the advantages and disadvantages of each type of fibre are discussed for various applications of geotextiles. The important functions of geotextiles, i.e. filtration, drainage, separation and reinforcement have been identified and have been related to several properties and major applications of geotextiles. Various geotextile properties, namely mechanical, hydraulic and chemical and their test methods have been critically discussed. A process-structure-property relationship for most commonly used geotextiles is also analysed. Furthermore, the design of a geotextile is of paramount importance for any civil engineering application. Thus, the design criteria for various functions of geotextiles have been addressed. Subsequently, the durability characteristics of geotextile have been introduced for analysing the performance over its lifetime.