Legal scholar Amanda L. Tyler discusses the history and future of habeas corpus in America and around the world. The concept of habeas corpus—literally, to receive and hold the body—empowers courts to protect the right of prisoners to know the basis on which they are being held by the government and grant prisoners their freedom when they are held unlawfully. It is no wonder that habeas corpus has long been considered essential to freedom. For nearly eight hundred years, the writ of habeas corpus has limited the executive in the Anglo-American legal tradition from imprisoning citizens and subjects with impunity. Writing in the eighteenth century, the widely influential English jurist and commentator William Blackstone declared the writ a "bulwark" of personal liberty. Across the Atlantic, in the leadup to the American Revolution, the Continental Congress declared that the habeas privilege and the right to trial by jury were among the most important rights in a free society. This Very Short Introduction chronicles the storied writ of habeas corpus and how its common law and statutory origins spread from England throughout the British Empire and beyond, witnessing its use today around the world in nations as varied as Canada, Israel, India, and South Korea. Beginning with the English origins of the writ, the book traces its historical development both as a part of the common law and as a parliamentary creation born out of the English Habeas Corpus Act of 1679, a statute that so dramatically limited the executive's power to detain that Blackstone called it no less than a "second Magna Carta." The book then takes the story forward to explore how the writ has functioned in the centuries since, including its controversial suspension by President Abraham Lincoln during the Civil War. It also analyzes the major role habeas corpus has played in such issues as the World War II incarceration of Japanese Americans and the US Supreme Court's recognition during the War on Terror of the concept of a "citizen enemy combatant." Looking ahead the story told in these pages reveals the immense challenges that the habeas privilege faces today and suggests that in confronting them, we would do well to remember how the habeas privilege brought even the king of England to his knees before the law.