Recent measurements have set a new record for the superconducting transition temperature (Tc ) at which a material losses electrical resistivity and exhibits ideal diamagnetism. Theory-oriented experiments show that the compressed hydride of Group VI (hydrogen sulfide, H3S) exhibits a superconducting state at 203 K. Moreover, a Group V hydride (phosphorus hydride, PH3) has also been studied and its Tc reached a maximum of 103 K. The experimental realisation of the superconductivity in H3S and PH3 inspired us to search for other hydride superconductors. Herein, we report theoretical studies of the electronic, vibrational, and superconducting properties of hydrogenated chlorine (H3Cl, representative of the Group VII hydride). First-principles calculations performed for H3Cl in the pressure range 150-250 GPa show that the investigated phase has a large electron-phonon coupling parameter and the resulting application of the Migdal-Eliashberg formalism yields a remarkably high superconducting temperature of 198 K at 150 GPa.