In this study, a novel multi-band metamaterial absorber has been proposed which is ultra-thin, compact, polarisation-insensitive and wide-angle absorptive. The proposed structure comprises two concentric metallic rings printed on a dielectric substrate which is backed by a metal ground plane. The proposed structure exhibits four distinct absorption peaks at 4.11, 7.91, 10.13 and 11.51 GHz with peak absorptivities of 98.81, 99.68, 99.98 and 99.34%, respectively, under normal incidence. The designed absorber is polarisation insensitive due to four-fold symmetry, which has been confirmed by simulation and measurement studies. Moreover, the structure shows high absorption (over 90%) for oblique incident angles up to 45 degrees for both transverse-electric and transverse-magnetic polarisations. The surface current distributions at the four absorption frequencies have been illustrated to explain the absorption mechanism of the structure. In addition, several parametric variations are performed to observe the effects of the geometrical dimensions on the absorption performance. The free space measurement method has been utilised to measure the responses of the fabricated structure, which are in good agreement with the simulated results. The proposed ultra-thin (approximate to 0.013(0) thin corresponding to lowest absorption frequency) absorber is anticipated to be useful in various potential applications like stealth technology, electromagnetic interference, electromagnetic compatibility and wireless communication.