Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online.Terahertz metamaterials are metamaterials which interact at terahertz frequencies. For research or applications of the terahertz range for metmaterials and other materials the frequency range is usually defined as 0.1 to 10 THz. This corresponds to the submillimeter wavelengths between 1 mm (EHF band) and 0.1 mm (long-wavelength edge of far-infrared light). Because applications of frequencies in the terahertz radiation range hold the promise of efficient advancement in important technologies, it has been important to find natural materials, or else, develop artificially constructed materials that have the desired electromagnetic response. Currently, a fundamental lack in naturally occurring materials that allow for the desired electromagnetic response has led to constructing artificial materials.