This book in the Library Futures Series examines blockchain technology, a concept with far-reaching implications for the future of the information professions. Blockchain uses a distributed database (multiple devices not connected to a common processor) that organizes data into records (blocks) that have cryptographic validation. The data are timestamped and linked to previous records so that they can only be changed by those who own the encryption keys to write to the files. In this book, the editors offer a primer of what librarians and information professionals need to understand about blockchain technology. Several speculative visions for how blockchain could support the core work of libraries are included to help librarians understand the possibilities for improved operations and services. Featuring essays from a range of information professionals who have interest and experience in blockchain technologies, this book presents valuable ideas for exploration relevant to everyone interested in the future of librarianship.