A flexible and twistable terahertz waveguide assembly has a flexible waveguide cable with waveguide flange connectors at its ends. The flexible waveguide cable comprises a segmented tube of a plurality of tube segments which are connected to each other. The tube encloses a dielectric waveguide which is held by means of threads (filaments) at the center of the tube. The individual segments are tiltable and/or pivotable against each other, allowing bending and twisting of the waveguide cable.