The extracellular matrix (ECM) is a master regulator of cellular phenotype and behaviour. It plays a critical role in both normal tissue homeostasis and pathological disease progression. Both the biochemical and biomechanical properties of the ECM contribute to modulating the behaviour of resident cells and are more than just passive bystanders. In tissue diseases such as cancer, the ECM undergoes significant change. These changes, driven by resident tumour cells, feed into the pathological progression of the disease. As such, changes in the ECM mark significant transition events in disease progression. Understanding how the changing ECM facilitates tumour progression and metastasis is an important step in the development of new therapeutic approaches for the treatment of cancer.