In the present study, as-synthesized pure ammonium manganese phosphate hydrate (AMP) is infused with rGO(x) variate (X-mg = 25, 50, 75, 100) and four different hybrid composites (AMPG1, AMPG2, AMPG3 and AMPG4) have been synthesized by facile microwave route. The XRD results show two prominent peaks, one at 2 theta = 10.04 degrees (010) and other at 2 theta = 31.3 degrees (200) in all AMPGs. The Debye-Scherrer's calculations show minimum crystallite size only for AMPG2 (80.9 nm). The Raman study confirms the rGO presence in AMPG2. The XPS confirms the existence of Mn as Mn2+ in AMPG2. The SEM /HR-TEM shows a cluster of uniform rectangular flake slabs only for AMPG2. The CV reveals that pure AMP and AMPGs exhibit pseudocapacitance. The GCD shows higher specific capacitance of 705 F g(-1) at a current density of 1 A g(-1) for AMPG2. The AMPG2/ /rGO hybrid device at 3 M aqueous H2SO4 shows higher specific capacitance of 336 F g(-1) at 1 A g(-1) in the potential window 0-1.8 volts, and even after 5000 cycles, the device retained 80% of its specific capacitance. The reason may be due to mapping of optimal concentration of rGO (50 mg) with PO43- and NH4+ of AMP by forming strong coordination for better activation sites for ion mobility. The energy and power densities of AMPG2/ /rGO device are 151 Wh kg(-1) and 448 W kg(-1) at 1 A g(-1), which are reported for the first time for highenergy supercapacitor applications. [GRAPHICS] .