Spin angular momentum of photons, and the associated polarisation of light, has been known of for many years. However, it is only during the 1990s and early 2000s that physically realisable laboratory light beams have been used to study the orbital angular momentum of light. In many respects orbital and spin angular momentum behave in a similar manner, but they differ significantly in others. In particular, orbital angular momentum offers exciting new possibilities with respect to the optical manipulation of matter, and to the study of the entanglement of photons. Optical Angular Momentum brings together 44 papers, reproduced over eight chapters, offering a comprehensive overview of the subject as it has developed. In each chapter the editors have written a concise introduction putting the selected papers into context and outlining the key articles associated with this aspect of the subject. The volume chronicles the first decade of this subject and gives a definitive statement of the status of all aspects of optical angular momentum.