Current paradigms of cancer-centric therapeutics are usually not sufficient to eradicate the malignancy, as the cancer stroma may prompt tumour relapse and therapeutic resistance. Among all the stromal cells that populate the tumour microenvironment, cancer-associated fibroblasts (CAFs) are the most abundant and are critically involved in cancer progression. CAFs regulate the biology of tumour cells and other stromal cells via cell–cell contact, releasing numerous regulatory factors and synthesizing and remodelling the extracellular matrix, and thus these cells affect cancer initiation and development. The recent characterization of CAFs based on specific cell surface markers not only deepens our insight into their phenotypic heterogeneity and functional diversity but also brings CAF-targeting therapies for cancer treatment onto the agenda. In this Review, we discuss the current knowledge of biological hallmarks, cellular origins, phenotypical plasticity and functional heterogeneity of CAFs and underscore their contribution to cancer progression. Moreover, we highlight relevant translational advances and potential therapeutic strategies that target CAFs for cancer treatment.