An innovative arrangement to provide a wide range of applications with ultra-wide band (UWB)-multiple input multiple output (MIMO) is suggested. The challenges, in practice, in implementing the design are wider bandwidth and substantial separation between the MIMO elements. Compactness is also one of the key role in designing the UWB-MIMO antenna. For portable UWB applications, this research provides a compact UWB-MIMO design with an excellent isolation level. Two rectangular elements with narrow slots on the radiating elements provide an excellent bandwidth in the UWB, 3.1-10.6 GHz. The proposed design is simulated using HFSS with substrate FR-4 epoxy. The proposed design uses a decoupling structure of elliptical shape on the partial ground to achieve better isolation improvement >15 dB in the entire UWB range. The proposed design exhibits multiband characteristics. The design exhibits compactness in size with 42 x 30 x 1.6 mm(3)and can be utilized for portable mobile applications. This design provides excellent performance metrics based on return loss (S-11 < -10 dB), isolation (S-12 < -15 dB), channel capacity loss (CCL < 0.001), total active reflection coefficient (TARC < -10 dB), diversity gain (DG > 9.998), radiation efficiency, patterns, peak gain (appox. 4.5), and correlation coefficient (ECC < 0.004).<br />