Flax fibres have been used by humans for approximately 10,000 years. With time, the geographic area of production and cultivation has changed, as have the applications of flax fibres; from clothing to sails and paintings from antiquity, to automotive, fashion, and design applications in the contemporary era. The degradation process of flax fibres is the same for both ancient and modern objects made from this polysaccharidic material. This review, focusing on the cultural heritage field, after a brief description of flax plants and fibres, retraces the history of their use through Europe and the Near East, and discusses the evolution of extraction methods with human progress. Furthermore, the most important mechanisms of flax fibre degradation and the characterisation techniques currently in use are described. This study highlights the constructive interchange between engineering and cultural heritage that can be realised through a continuous comparison of antiquity and the contemporary era.