A new geometry of ultra-wideband (UWB) hollow dielectric resonator antenna (DRA) has been designed, simulated, and fabricated. The antenna consists of a rectangular dielectric resonator and excited by a transformer type microstrip feedline. A hollow cylindrical-shaped structure is extracted from a rectangular DR to improve the gain and impedance bandwidth of the antenna. The present work shows that the shifting within the UWB range along with the gain enhancement is observed by increased diameter of the hollow structure and the use of defective ground structure in the ground plane. The antenna provides four different radiating modes, namely TE_11d at 3.8 GHz, TE_22d at 6.4 GHz, TE₂₃₁^Z at 8.8 GHz, and TE_33d at 10 GHz that support to give widen impedance bandwidth. The simulated and measured results are in good agreement as an impedance bandwidth of 104.09% (3.28 to 10.4 GHz) and 103.86% along with a peak gain of 7.2 dB.