The author describes superfluidity as the jewel in the crown of low temperature physics. At low enough temperatures, every substance in thermal equilibrium must become ordered. Since some materials remain fluid to the lowest temperatures, it is a fascinating question as to how this ordering can take place. The book assumes some basic knowledge of quantum, statistical and thermal physics, and builds on this background to give a readable introduction to the three superfluids of low temperature physics. The book emphasizes physical principles rather than technical detail, with the aim of introducing the subject in an accessible yet authoritative way to final year undergraduates or starting graduate students.