Uridine is the ubiquitous nucleoside form of the RNA base uracil. It occupies a prominent 'hub' position in energy metabolism; for example, it is metabolically linked to de novo pyrimidine biosynthesis and glycolysis and biologically linked to diverse processes, such as RNA synthesis/degradation and glycosylation. It is a vital interorgan 'currency' nutrient readily imported by mammalian cells, and its supplementation can exert both cytoprotective and toxic effects, for which the underlying mechanisms are poorly understood. Importantly, it is a route by which the decay of RNA can be repurposed as an alternative fuel source under nutrient-limiting conditions to aid in tumor initiation, development and metastasis. Here we explain how the upstream inputs and downstream metabolic fates of uridine influence cancer traits and illustrate both established and hypothetical strategies targeting uridine metabolism for cancer therapy.