The THz waveguides disclosed herein are used to transmit signals having a THz frequency in the range from 0.1 THz to 10 THz and include an alumina core surrounded by an optional cladding. The core may have a diameter (D1) in the range from 10 μm to 500 μm and may be comprised of a ceramic ribbon having a dielectric constant (Dk). The optional cladding may have a dielectric constant (Dk) less than the core. The THz waveguides can be formed using a continuous firing process and nano-perforation technology that enables access to a wide form factor range. In one example, rectangular waveguides, or ribbons, may be fabricated in the 10 μm to 200 μm thick range at widths in the range from sub-millimeters to several meters and lengths in the range from millimeters to several hundred meters.