This book provides a practical guide to terahertz electronics, especially for readers with an electronics background. The author guides readers through the all the key concepts of terahertz electronics, including terahertz sources, detectors, and waveguides, together with reviews on key terahertz applications on spectroscopy, imaging, communication, and radar. This book will serve as a handy reference for graduate students and engineers in the field of terahertz with a viewpoint from electronics. It presents the topic of terahertz from electronics viewpoint; is designed to be particularly helpful for the readers familiar with semiconductor devices and circuits; enables optics-based terahertz researchers to understand terahertz electronics; and is based on the author's extensive experience from both industry and academia.