Axions occupy a special place in modern theoretical physics. As part of the most credible solution to the strong CP problem, they are a very plausible extension of the known physics of the standard model. Simultaneously, they are also a generic prediction of the exotic physics of compactifications in string and M theory. Their influence appears across a wide range of epochs, from the inflation and cosmology of the early universe, to late time aspects such as large scale structure, solar physics, dark matter and even dark energy. Furthermore, given their typically light mass, and the array of ongoing and planned experimental efforts into their discovery, the era of axion physics may not be far off. We give a pedagogical overview of this topic, and discuss future prospects for axion physics.