Major enterprises shape our lives in countless ways: big tech and 'surveillance media' that affect democratic debate, algorithms that influence online shopping, transport to work and home, energy and agriculture corporations that drive climate damage, and public services that provide our education, health, water, and housing. The twentieth century experienced swings between private and public ownership, between capitalism and socialism, without any settled, principled outcome, and without settling major questions of how enterprises should be financed, governed and the rights we have in them. This book's main question is 'are there principles of enterprise law', and, if they are missing, 'what principles of enterprise law should there be'? Principles of Enterprise Law gives a functional account of the 'general' enterprise laws of companies, investment, labour, competition and insolvency, before moving into specific enterprises, from universities to the military. It is an original guide to our economic constitution and human rights.