Radiation from astronomical objects generally shows some degree of polarization. Although this polarized radiation is usually only a small fraction of the total radiation, it often carries a wealth of information on the physical state and geometry of the emitting object and intervening material. Measurement of this polarized radiation is central to much modern astrophysical research. This handy volume provides a clear, comprehensive and concise introduction to astronomical polarimetry at all wavelengths. Starting from first principles and a simple physical picture of polarized radiation, the reader is introduced to all the key topics, including Stokes parameters, applications of polarimetry in astronomy, polarization algebra, polarization errors and calibration methods, and a selection of instruments (from radio to X-ray). The book is rounded off with a number of useful case studies, a collection of exercises, an extensive list of further reading and an informative index. This review of all aspects of astronomical polarization provides both an essential introduction for graduate students, and a valuable reference for practising astronomers.