Chipless RFID Authentication examines the development of highly secure product authentication systems for manufactured products by using chipless radio frequency identification (RFID) technology. The absence of a chip and its compatibility with mass production make chipless RFID an alternative to barcodes. This book discusses how, by using natural randomness inherent to the fabrication process, each chipless RFID tag has a unique signature that can never be reproduced, even if someone tries to copy the label. The book first explores the state-of-the-art of existing authentication and anti-counterfeiting methods based on their security level. Next, a methodology describing the characterization of chipless RFID tags for the authentication application is presented, followed by a discussion of the extraction of aspect-independent parameters for chipless RFID tags. After proposing designs for the tags, the book presents the realization and characterization of the labels (which exhibit naturally occurring randomness) for authentication, using printed circuit boards and inkjet printing on polyethylene terephthalate.