With Wireless communications in the 0.1–10 TeraHertz (THz) band are envisioned as one of the key enablers towards ubiquitous wireless communications beyond 5G accommodating a massive number of connected devices and ultra-high user data rates in the order of Tera-bit-per-second. The THz band is located between the millimeter-wave (mmWave) and the far infrared (IR) band and still considered as one of the least investigated and exploited regions in the electromagnetic spectrum, although it offers much higher bandwidth than the mmWave range and more favorable propagation conditions than the IR band. Recently, significant progress has been made with respect to THz devices based on different technologies, and commercial THz systems are anticipated to become a reality in the near future.