This book Tube Forming systematically describes the manufacturing techniques used to process tubes into finished products. It provides a comprehensive overview of tube processing technologies, including materials, tribology, cutting, bending, flaring, necking, bulging, piercing, and joining. While textbooks on primary tube processing exist, there is no comprehensive textbook that covers secondary tube processing. With the increasing use of tubes as structural components in office equipment, automobiles, and other fields, there has been a growing demand for secondary tube processing technologies that allow for more complex forming, including tube hydroforming. This textbook systematically incorporates both fundamental and the latest technologies in response to these demands for greater complexity, lighter weight, and higher strength in tube processing. The textbook is authored by university professors and industry engineers, and it systematically covers everything from basic theory and processing methods to practical examples and important considerations during processing. As a result, it is a valuable resource not only for undergraduate and graduate students but also for working engineers. While various information can be obtained through internet searches, the quality of online information varies greatly, requiring users to have the ability to judge its quality. Although special issues in academic journals provide high-quality information, they typically consist of fragmented content, making them less suitable for mastering the technology. Therefore, this textbook was compiled as a systematic and high-quality resource. This textbook was originally published in Japanese in 2019, and it has now been translated into English to make it accessible to readers outside Japan.